aboutsummaryrefslogblamecommitdiffstats
path: root/vendor/sabre/dav/docs/rfc5545.txt
blob: 47ea31d6092122057c57109ce51f8369202e034a (plain) (tree)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
5007
5008
5009
5010
5011
5012
5013
5014
5015
5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064
5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
5076
5077
5078
5079
5080
5081
5082
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
5103
5104
5105
5106
5107
5108
5109
5110
5111
5112
5113
5114
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
5374
5375
5376
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
5413
5414
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434
5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466
5467
5468
5469
5470
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
5499
5500
5501
5502
5503
5504
5505
5506
5507
5508
5509
5510
5511
5512
5513
5514
5515
5516
5517
5518
5519
5520
5521
5522
5523
5524
5525
5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546
5547
5548
5549
5550
5551
5552
5553
5554
5555
5556
5557
5558
5559
5560
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
5583
5584
5585
5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
5599
5600
5601
5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626
5627
5628
5629
5630
5631
5632
5633
5634
5635
5636
5637
5638
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
5686
5687
5688
5689
5690
5691
5692
5693
5694
5695
5696
5697
5698
5699
5700
5701
5702
5703
5704
5705
5706
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
5721
5722
5723
5724
5725
5726
5727
5728
5729
5730
5731
5732
5733
5734
5735
5736
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
5756
5757
5758
5759
5760
5761
5762
5763
5764
5765
5766
5767
5768
5769
5770
5771
5772
5773
5774
5775
5776
5777
5778
5779
5780
5781
5782
5783
5784
5785
5786
5787
5788
5789
5790
5791
5792
5793
5794
5795
5796
5797
5798
5799
5800
5801
5802
5803
5804
5805
5806
5807
5808
5809
5810
5811
5812
5813
5814
5815
5816
5817
5818
5819
5820
5821
5822
5823
5824
5825
5826
5827
5828
5829
5830
5831
5832
5833
5834
5835
5836
5837
5838
5839
5840
5841
5842
5843
5844
5845
5846
5847
5848
5849
5850
5851
5852
5853
5854
5855
5856
5857
5858
5859
5860
5861
5862
5863
5864
5865
5866
5867
5868
5869
5870
5871
5872
5873
5874
5875
5876
5877
5878
5879
5880
5881
5882
5883
5884
5885
5886
5887
5888
5889
5890
5891
5892
5893
5894
5895
5896
5897
5898
5899
5900
5901
5902
5903
5904
5905
5906
5907
5908
5909
5910
5911
5912
5913
5914
5915
5916
5917
5918
5919
5920
5921
5922
5923
5924
5925
5926
5927
5928
5929
5930
5931
5932
5933
5934
5935
5936
5937
5938
5939
5940
5941
5942
5943
5944
5945
5946
5947
5948
5949
5950
5951
5952
5953
5954
5955
5956
5957
5958
5959
5960
5961
5962
5963
5964
5965
5966
5967
5968
5969
5970
5971
5972
5973
5974
5975
5976
5977
5978
5979
5980
5981
5982
5983
5984
5985
5986
5987
5988
5989
5990
5991
5992
5993
5994
5995
5996
5997
5998
5999
6000
6001
6002
6003
6004
6005
6006
6007
6008
6009
6010
6011
6012
6013
6014
6015
6016
6017
6018
6019
6020
6021
6022
6023
6024
6025
6026
6027
6028
6029
6030
6031
6032
6033
6034
6035
6036
6037
6038
6039
6040
6041
6042
6043
6044
6045
6046
6047
6048
6049
6050
6051
6052
6053
6054
6055
6056
6057
6058
6059
6060
6061
6062
6063
6064
6065
6066
6067
6068
6069
6070
6071
6072
6073
6074
6075
6076
6077
6078
6079
6080
6081
6082
6083
6084
6085
6086
6087
6088
6089
6090
6091
6092
6093
6094
6095
6096
6097
6098
6099
6100
6101
6102
6103
6104
6105
6106
6107
6108
6109
6110
6111
6112
6113
6114
6115
6116
6117
6118
6119
6120
6121
6122
6123
6124
6125
6126
6127
6128
6129
6130
6131
6132
6133
6134
6135
6136
6137
6138
6139
6140
6141
6142
6143
6144
6145
6146
6147
6148
6149
6150
6151
6152
6153
6154
6155
6156
6157
6158
6159
6160
6161
6162
6163
6164
6165
6166
6167
6168
6169
6170
6171
6172
6173
6174
6175
6176
6177
6178
6179
6180
6181
6182
6183
6184
6185
6186
6187
6188
6189
6190
6191
6192
6193
6194
6195
6196
6197
6198
6199
6200
6201
6202
6203
6204
6205
6206
6207
6208
6209
6210
6211
6212
6213
6214
6215
6216
6217
6218
6219
6220
6221
6222
6223
6224
6225
6226
6227
6228
6229
6230
6231
6232
6233
6234
6235
6236
6237
6238
6239
6240
6241
6242
6243
6244
6245
6246
6247
6248
6249
6250
6251
6252
6253
6254
6255
6256
6257
6258
6259
6260
6261
6262
6263
6264
6265
6266
6267
6268
6269
6270
6271
6272
6273
6274
6275
6276
6277
6278
6279
6280
6281
6282
6283
6284
6285
6286
6287
6288
6289
6290
6291
6292
6293
6294
6295
6296
6297
6298
6299
6300
6301
6302
6303
6304
6305
6306
6307
6308
6309
6310
6311
6312
6313
6314
6315
6316
6317
6318
6319
6320
6321
6322
6323
6324
6325
6326
6327
6328
6329
6330
6331
6332
6333
6334
6335
6336
6337
6338
6339
6340
6341
6342
6343
6344
6345
6346
6347
6348
6349
6350
6351
6352
6353
6354
6355
6356
6357
6358
6359
6360
6361
6362
6363
6364
6365
6366
6367
6368
6369
6370
6371
6372
6373
6374
6375
6376
6377
6378
6379
6380
6381
6382
6383
6384
6385
6386
6387
6388
6389
6390
6391
6392
6393
6394
6395
6396
6397
6398
6399
6400
6401
6402
6403
6404
6405
6406
6407
6408
6409
6410
6411
6412
6413
6414
6415
6416
6417
6418
6419
6420
6421
6422
6423
6424
6425
6426
6427
6428
6429
6430
6431
6432
6433
6434
6435
6436
6437
6438
6439
6440
6441
6442
6443
6444
6445
6446
6447
6448
6449
6450
6451
6452
6453
6454
6455
6456
6457
6458
6459
6460
6461
6462
6463
6464
6465
6466
6467
6468
6469
6470
6471
6472
6473
6474
6475
6476
6477
6478
6479
6480
6481
6482
6483
6484
6485
6486
6487
6488
6489
6490
6491
6492
6493
6494
6495
6496
6497
6498
6499
6500
6501
6502
6503
6504
6505
6506
6507
6508
6509
6510
6511
6512
6513
6514
6515
6516
6517
6518
6519
6520
6521
6522
6523
6524
6525
6526
6527
6528
6529
6530
6531
6532
6533
6534
6535
6536
6537
6538
6539
6540
6541
6542
6543
6544
6545
6546
6547
6548
6549
6550
6551
6552
6553
6554
6555
6556
6557
6558
6559
6560
6561
6562
6563
6564
6565
6566
6567
6568
6569
6570
6571
6572
6573
6574
6575
6576
6577
6578
6579
6580
6581
6582
6583
6584
6585
6586
6587
6588
6589
6590
6591
6592
6593
6594
6595
6596
6597
6598
6599
6600
6601
6602
6603
6604
6605
6606
6607
6608
6609
6610
6611
6612
6613
6614
6615
6616
6617
6618
6619
6620
6621
6622
6623
6624
6625
6626
6627
6628
6629
6630
6631
6632
6633
6634
6635
6636
6637
6638
6639
6640
6641
6642
6643
6644
6645
6646
6647
6648
6649
6650
6651
6652
6653
6654
6655
6656
6657
6658
6659
6660
6661
6662
6663
6664
6665
6666
6667
6668
6669
6670
6671
6672
6673
6674
6675
6676
6677
6678
6679
6680
6681
6682
6683
6684
6685
6686
6687
6688
6689
6690
6691
6692
6693
6694
6695
6696
6697
6698
6699
6700
6701
6702
6703
6704
6705
6706
6707
6708
6709
6710
6711
6712
6713
6714
6715
6716
6717
6718
6719
6720
6721
6722
6723
6724
6725
6726
6727
6728
6729
6730
6731
6732
6733
6734
6735
6736
6737
6738
6739
6740
6741
6742
6743
6744
6745
6746
6747
6748
6749
6750
6751
6752
6753
6754
6755
6756
6757
6758
6759
6760
6761
6762
6763
6764
6765
6766
6767
6768
6769
6770
6771
6772
6773
6774
6775
6776
6777
6778
6779
6780
6781
6782
6783
6784
6785
6786
6787
6788
6789
6790
6791
6792
6793
6794
6795
6796
6797
6798
6799
6800
6801
6802
6803
6804
6805
6806
6807
6808
6809
6810
6811
6812
6813
6814
6815
6816
6817
6818
6819
6820
6821
6822
6823
6824
6825
6826
6827
6828
6829
6830
6831
6832
6833
6834
6835
6836
6837
6838
6839
6840
6841
6842
6843
6844
6845
6846
6847
6848
6849
6850
6851
6852
6853
6854
6855
6856
6857
6858
6859
6860
6861
6862
6863
6864
6865
6866
6867
6868
6869
6870
6871
6872
6873
6874
6875
6876
6877
6878
6879
6880
6881
6882
6883
6884
6885
6886
6887
6888
6889
6890
6891
6892
6893
6894
6895
6896
6897
6898
6899
6900
6901
6902
6903
6904
6905
6906
6907
6908
6909
6910
6911
6912
6913
6914
6915
6916
6917
6918
6919
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930
6931
6932
6933
6934
6935
6936
6937
6938
6939
6940
6941
6942
6943
6944
6945
6946
6947
6948
6949
6950
6951
6952
6953
6954
6955
6956
6957
6958
6959
6960
6961
6962
6963
6964
6965
6966
6967
6968
6969
6970
6971
6972
6973
6974
6975
6976
6977
6978
6979
6980
6981
6982
6983
6984
6985
6986
6987
6988
6989
6990
6991
6992
6993
6994
6995
6996
6997
6998
6999
7000
7001
7002
7003
7004
7005
7006
7007
7008
7009
7010
7011
7012
7013
7014
7015
7016
7017
7018
7019
7020
7021
7022
7023
7024
7025
7026
7027
7028
7029
7030
7031
7032
7033
7034
7035
7036
7037
7038
7039
7040
7041
7042
7043
7044
7045
7046
7047
7048
7049
7050
7051
7052
7053
7054
7055
7056
7057
7058
7059
7060
7061
7062
7063
7064
7065
7066
7067
7068
7069
7070
7071
7072
7073
7074
7075
7076
7077
7078
7079
7080
7081
7082
7083
7084
7085
7086
7087
7088
7089
7090
7091
7092
7093
7094
7095
7096
7097
7098
7099
7100
7101
7102
7103
7104
7105
7106
7107
7108
7109
7110
7111
7112
7113
7114
7115
7116
7117
7118
7119
7120
7121
7122
7123
7124
7125
7126
7127
7128
7129
7130
7131
7132
7133
7134
7135
7136
7137
7138
7139
7140
7141
7142
7143
7144
7145
7146
7147
7148
7149
7150
7151
7152
7153
7154
7155
7156
7157
7158
7159
7160
7161
7162
7163
7164
7165
7166
7167
7168
7169
7170
7171
7172
7173
7174
7175
7176
7177
7178
7179
7180
7181
7182
7183
7184
7185
7186
7187
7188
7189
7190
7191
7192
7193
7194
7195
7196
7197
7198
7199
7200
7201
7202
7203
7204
7205
7206
7207
7208
7209
7210
7211
7212
7213
7214
7215
7216
7217
7218
7219
7220
7221
7222
7223
7224
7225
7226
7227
7228
7229
7230
7231
7232
7233
7234
7235
7236
7237
7238
7239
7240
7241
7242
7243
7244
7245
7246
7247
7248
7249
7250
7251
7252
7253
7254
7255
7256
7257
7258
7259
7260
7261
7262
7263
7264
7265
7266
7267
7268
7269
7270
7271
7272
7273
7274
7275
7276
7277
7278
7279
7280
7281
7282
7283
7284
7285
7286
7287
7288
7289
7290
7291
7292
7293
7294
7295
7296
7297
7298
7299
7300
7301
7302
7303
7304
7305
7306
7307
7308
7309
7310
7311
7312
7313
7314
7315
7316
7317
7318
7319
7320
7321
7322
7323
7324
7325
7326
7327
7328
7329
7330
7331
7332
7333
7334
7335
7336
7337
7338
7339
7340
7341
7342
7343
7344
7345
7346
7347
7348
7349
7350
7351
7352
7353
7354
7355
7356
7357
7358
7359
7360
7361
7362
7363
7364
7365
7366
7367
7368
7369
7370
7371
7372
7373
7374
7375
7376
7377
7378
7379
7380
7381
7382
7383
7384
7385
7386
7387
7388
7389
7390
7391
7392
7393
7394
7395
7396
7397
7398
7399
7400
7401
7402
7403
7404
7405
7406
7407
7408
7409
7410
7411
7412
7413
7414
7415
7416
7417
7418
7419
7420
7421
7422
7423
7424
7425
7426
7427
7428
7429
7430
7431
7432
7433
7434
7435
7436
7437
7438
7439
7440
7441
7442
7443
7444
7445
7446
7447
7448
7449
7450
7451
7452
7453
7454
7455
7456
7457
7458
7459
7460
7461
7462
7463
7464
7465
7466
7467
7468
7469
7470
7471
7472
7473
7474
7475
7476
7477
7478
7479
7480
7481
7482
7483
7484
7485
7486
7487
7488
7489
7490
7491
7492
7493
7494
7495
7496
7497
7498
7499
7500
7501
7502
7503
7504
7505
7506
7507
7508
7509
7510
7511
7512
7513
7514
7515
7516
7517
7518
7519
7520
7521
7522
7523
7524
7525
7526
7527
7528
7529
7530
7531
7532
7533
7534
7535
7536
7537
7538
7539
7540
7541
7542
7543
7544
7545
7546
7547
7548
7549
7550
7551
7552
7553
7554
7555
7556
7557
7558
7559
7560
7561
7562
7563
7564
7565
7566
7567
7568
7569
7570
7571
7572
7573
7574
7575
7576
7577
7578
7579
7580
7581
7582
7583
7584
7585
7586
7587
7588
7589
7590
7591
7592
7593
7594
7595
7596
7597
7598
7599
7600
7601
7602
7603
7604
7605
7606
7607
7608
7609
7610
7611
7612
7613
7614
7615
7616
7617
7618
7619
7620
7621
7622
7623
7624
7625
7626
7627
7628
7629
7630
7631
7632
7633
7634
7635
7636
7637
7638
7639
7640
7641
7642
7643
7644
7645
7646
7647
7648
7649
7650
7651
7652
7653
7654
7655
7656
7657
7658
7659
7660
7661
7662
7663
7664
7665
7666
7667
7668
7669
7670
7671
7672
7673
7674
7675
7676
7677
7678
7679
7680
7681
7682
7683
7684
7685
7686
7687
7688
7689
7690
7691
7692
7693
7694
7695
7696
7697
7698
7699
7700
7701
7702
7703
7704
7705
7706
7707
7708
7709
7710
7711
7712
7713
7714
7715
7716
7717
7718
7719
7720
7721
7722
7723
7724
7725
7726
7727
7728
7729
7730
7731
7732
7733
7734
7735
7736
7737
7738
7739
7740
7741
7742
7743
7744
7745
7746
7747
7748
7749
7750
7751
7752
7753
7754
7755
7756
7757
7758
7759
7760
7761
7762
7763
7764
7765
7766
7767
7768
7769
7770
7771
7772
7773
7774
7775
7776
7777
7778
7779
7780
7781
7782
7783
7784
7785
7786
7787
7788
7789
7790
7791
7792
7793
7794
7795
7796
7797
7798
7799
7800
7801
7802
7803
7804
7805
7806
7807
7808
7809
7810
7811
7812
7813
7814
7815
7816
7817
7818
7819
7820
7821
7822
7823
7824
7825
7826
7827
7828
7829
7830
7831
7832
7833
7834
7835
7836
7837
7838
7839
7840
7841
7842
7843
7844
7845
7846
7847
7848
7849
7850
7851
7852
7853
7854
7855
7856
7857
7858
7859
7860
7861
7862
7863
7864
7865
7866
7867
7868
7869
7870
7871
7872
7873
7874
7875
7876
7877
7878
7879
7880
7881
7882
7883
7884
7885
7886
7887
7888
7889
7890
7891
7892
7893
7894
7895
7896
7897
7898
7899
7900
7901
7902
7903
7904
7905
7906
7907
7908
7909
7910
7911
7912
7913
7914
7915
7916
7917
7918
7919
7920
7921
7922
7923
7924
7925
7926
7927
7928
7929
7930
7931
7932
7933
7934
7935
7936
7937
7938
7939
7940
7941
7942
7943
7944
7945
7946
7947
7948
7949
7950
7951
7952
7953
7954
7955
7956
7957
7958
7959
7960
7961
7962
7963
7964
7965
7966
7967
7968
7969
7970
7971
7972
7973
7974
7975
7976
7977
7978
7979
7980
7981
7982
7983
7984
7985
7986
7987
7988
7989
7990
7991
7992
7993
7994
7995
7996
7997
7998
7999
8000
8001
8002
8003
8004
8005
8006
8007
8008
8009
8010
8011
8012
8013
8014
8015
8016
8017
8018
8019
8020
8021
8022
8023
8024
8025
8026
8027
8028
8029
8030
8031
8032
8033
8034
8035
8036
8037
8038
8039
8040
8041
8042
8043
8044
8045
8046
8047
8048
8049
8050
8051
8052
8053
8054
8055
8056
8057
8058
8059
8060
8061
8062
8063
8064
8065
8066
8067
8068
8069
8070
8071
8072
8073
8074
8075
8076
8077
8078
8079
8080
8081
8082
8083
8084
8085
8086
8087
8088
8089
8090
8091
8092
8093
8094
8095
8096
8097
8098
8099
8100
8101
8102
8103
8104
8105
8106
8107
8108
8109
8110
8111
8112
8113
8114
8115
8116
8117
8118
8119
8120
8121
8122
8123
8124
8125
8126
8127
8128
8129
8130
8131
8132
8133
8134
8135
8136
8137
8138
8139
8140
8141
8142
8143
8144
8145
8146
8147
8148
8149
8150
8151
8152
8153
8154
8155
8156
8157
8158
8159
8160
8161
8162
8163
8164
8165
8166
8167
8168
8169
8170
8171
8172
8173
8174
8175
8176
8177
8178
8179
8180
8181
8182
8183
8184
8185
8186
8187
8188
8189
8190
8191
8192
8193
8194
8195
8196
8197
8198
8199
8200
8201
8202
8203
8204
8205
8206
8207
8208
8209
8210
8211
8212
8213
8214
8215
8216
8217
8218
8219
8220
8221
8222
8223
8224
8225
8226
8227
8228
8229
8230
8231
8232
8233
8234
8235
8236
8237
8238
8239
8240
8241
8242
8243
8244
8245
8246
8247
8248
8249
8250
8251
8252
8253
8254
8255
8256
8257
8258
8259
8260
8261
8262
8263
8264
8265
8266
8267
8268
8269
8270
8271
8272
8273
8274
8275
8276
8277
8278
8279
8280
8281
8282
8283
8284
8285
8286
8287
8288
8289
8290
8291
8292
8293
8294
8295
8296
8297
8298
8299
8300
8301
8302
8303
8304
8305
8306
8307
8308
8309
8310
8311
8312
8313
8314
8315
8316
8317
8318
8319
8320
8321
8322
8323
8324
8325
8326
8327
8328
8329
8330
8331
8332
8333
8334
8335
8336
8337
8338
8339
8340
8341
8342
8343
8344
8345
8346
8347
8348
8349
8350
8351
8352
8353
8354
8355
8356
8357
8358
8359
8360
8361
8362
8363
8364
8365
8366
8367
8368
8369
8370
8371
8372
8373
8374
8375
8376
8377
8378
8379
8380
8381
8382
8383
8384
8385
8386
8387
8388
8389
8390
8391
8392
8393
8394
8395
8396
8397
8398
8399
8400
8401
8402
8403
8404
8405
8406
8407
8408
8409
8410
8411
8412
8413
8414
8415
8416
8417
8418
8419
8420
8421
8422
8423
8424
8425
8426
8427
8428
8429
8430
8431
8432
8433
8434
8435
8436
8437
8438
8439
8440
8441
8442
8443
8444
8445
8446
8447
8448
8449
8450
8451
8452
8453
8454
8455
8456
8457
8458
8459
8460
8461
8462
8463
8464
8465
8466
8467
8468
8469
8470
8471
8472
8473
8474
8475
8476
8477
8478
8479
8480
8481
8482
8483
8484
8485
8486
8487
8488
8489
8490
8491
8492
8493
8494
8495
8496
8497
8498
8499
8500
8501
8502
8503
8504
8505
8506
8507
8508
8509
8510
8511
8512
8513
8514
8515
8516
8517
8518
8519
8520
8521
8522
8523
8524
8525
8526
8527
8528
8529
8530
8531
8532
8533
8534
8535
8536
8537
8538
8539
8540
8541
8542
8543
8544
8545
8546
8547
8548
8549
8550
8551
8552
8553
8554
8555
8556
8557
8558
8559
8560
8561
8562
8563
8564
8565
8566
8567
8568
8569
8570
8571
8572
8573
8574
8575
8576
8577
8578
8579
8580
8581
8582
8583
8584
8585
8586
8587
8588
8589
8590
8591
8592
8593
8594
8595
8596
8597
8598
8599
8600
8601
8602
8603
8604
8605
8606
8607
8608
8609
8610
8611
8612
8613
8614
8615
8616
8617
8618
8619
8620
8621
8622
8623
8624
8625
8626
8627
8628
8629
8630
8631
8632
8633
8634
8635
8636
8637
8638
8639
8640
8641
8642
8643
8644
8645
8646
8647
8648
8649
8650
8651
8652
8653
8654
8655
8656
8657
8658
8659
8660
8661
8662
8663
8664
8665
8666
8667
8668
8669
8670
8671
8672
8673
8674
8675
8676
8677
8678
8679
8680
8681
8682
8683
8684
8685
8686
8687
8688
8689
8690
8691
8692
8693
8694
8695
8696
8697
8698
8699
8700
8701
8702
8703
8704
8705
8706
8707
8708
8709
8710
8711
8712
8713
8714
8715
8716
8717
8718
8719
8720
8721
8722
8723
8724
8725
8726
8727
8728
8729
8730
8731
8732
8733
8734
8735
8736
8737
8738
8739
8740
8741
8742
8743
8744
8745
8746
8747
8748
8749
8750
8751
8752
8753
8754
8755
8756
8757
8758
8759
8760
8761
8762
8763
8764
8765
8766
8767
8768
8769
8770
8771
8772
8773
8774
8775
8776
8777
8778
8779
8780
8781
8782
8783
8784
8785
8786
8787
8788
8789
8790
8791
8792
8793
8794
8795
8796
8797
8798
8799
8800
8801
8802
8803
8804
8805
8806
8807
8808
8809
8810
8811
8812
8813
8814
8815
8816
8817
8818
8819
8820
8821
8822
8823
8824
8825
8826
8827
8828
8829
8830
8831
8832
8833
8834
8835
8836
8837
8838
8839
8840
8841
8842
8843
8844
8845
8846
8847
8848
8849
8850
8851
8852
8853
8854
8855
8856
8857
8858
8859
8860
8861
8862
8863
8864
8865
8866
8867
8868
8869
8870
8871
8872
8873
8874
8875
8876
8877
8878
8879
8880
8881
8882
8883
8884
8885
8886
8887
8888
8889
8890
8891
8892
8893
8894
8895
8896
8897
8898
8899
8900
8901
8902
8903
8904
8905
8906
8907
8908
8909
8910
8911
8912
8913
8914
8915
8916
8917
8918
8919
8920
8921
8922
8923
8924
8925
8926
8927
8928
8929
8930
8931
8932
8933
8934
8935
8936
8937
8938
8939
8940
8941
8942
8943
8944
8945
8946
8947
8948
8949
8950
8951
8952
8953
8954
8955
8956
8957
8958
8959
8960
8961
8962
8963
8964
8965
8966
8967
8968
8969
8970
8971
8972
8973
8974
8975
8976
8977
8978
8979
8980
8981
8982
8983
8984
8985
8986
8987
8988
8989
8990
8991
8992
8993
8994
8995
8996
8997
8998
8999
9000
9001
9002
9003
9004
9005
9006
9007
9008
9009
9010
9011
9012
9013
9014
9015
9016
9017
9018
9019
9020
9021
9022
9023
9024
9025
9026
9027
9028
9029
9030
9031
9032
9033
9034
9035
9036
9037
9038
9039
9040
9041
9042
9043
9044
9045
9046
9047
9048
9049
9050
9051
9052
9053
9054
9055
9056
9057
9058
9059
9060
9061
9062
9063
9064
9065
9066
9067
9068
9069
9070
9071
9072
9073
9074
9075
9076
9077
9078
9079
9080
9081
9082
9083
9084
9085
9086
9087
9088
9089
9090
9091
9092
9093
9094
9095
9096
9097
9098
9099
9100
9101
9102
9103
9104
9105
9106
9107
9108
9109
9110
9111
9112
9113
9114
9115
9116
9117
9118
9119
9120
9121
9122
9123
9124
9125
9126
9127
9128
9129
9130
9131
9132
9133
9134
9135
9136
9137
9138
9139
9140
9141
9142
9143
9144
9145
9146
9147
9148
9149
9150
9151
9152
9153
9154
9155
9156
9157
9158
9159
9160
9161
9162
9163
9164
9165
9166
9167
9168
9169
9170
9171
9172
9173
9174
9175
9176
9177
9178
9179
9180
9181
9182
9183
9184
9185
9186
9187
9188
9189
9190
9191
9192
9193
9194
9195
9196
9197
9198
9199
9200
9201
9202
9203
9204
9205
9206
9207
9208
9209
9210
9211
9212
9213
9214
9215
9216
9217
9218
9219
9220
9221
9222
9223
9224
9225
9226
9227
9228
9229
9230
9231
9232
9233
9234
9235
9236
9237
9238
9239
9240
9241
9242
9243
9244
9245
9246
9247
9248
9249
9250
9251
9252
9253
9254
9255
9256
9257
9258
9259
9260
9261
9262
9263
9264
9265
9266
9267
9268
9269
9270
9271
9272
9273
9274
9275
9276
9277
9278
9279
9280
9281
9282
9283
9284
9285
9286
9287
9288
9289
9290
9291
9292
9293
9294
9295
9296
9297
9298
9299
9300
9301
9302
9303
9304
9305
9306
9307
9308
9309
9310
9311
9312
9313
9314
9315
9316
9317
9318
9319
9320
9321
9322
9323
9324
9325
9326
9327
9328
9329
9330
9331
9332
9333
9334
9335
9336
9337
9338
9339
9340
9341
9342
9343
9344
9345
9346
9347
9348
9349
9350
9351
9352
9353
9354
9355
9356
9357
9358
9359
9360
9361
9362
9363
9364
9365
9366
9367
9368
9369
9370
9371
9372
9373
9374
9375
9376
9377
9378
9379
9380
9381
9382
9383
9384
9385
9386
9387
9388
9389
9390
9391
9392
9393
9394
9395
9396
9397
9398
9399
9400
9401
9402
9403
9404
9405
9406
9407
9408
9409
9410
9411


































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































                                                                        
Network Working Group                               B. Desruisseaux, Ed.
Request for Comments: 5545                                        Oracle
Obsoletes: 2445                                           September 2009
Category: Standards Track


     Internet Calendaring and Scheduling Core Object Specification
                              (iCalendar)

Abstract

This document defines the iCalendar data format for representing and
exchanging calendaring and scheduling information such as events,
to-dos, journal entries, and free/busy information, independent of any
particular calendar service or protocol.

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright and License Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format



Desruisseaux                Standards Track                     [Page 1]

RFC 5545                       iCalendar                  September 2009


   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Basic Grammar and Conventions . . . . . . . . . . . . . . . .   6
     2.1.  Formatting Conventions  . . . . . . . . . . . . . . . . .   6
     2.2.  Related Memos . . . . . . . . . . . . . . . . . . . . . .   7
   3.  iCalendar Object Specification  . . . . . . . . . . . . . . .   8
     3.1.  Content Lines . . . . . . . . . . . . . . . . . . . . . .   8
       3.1.1.  List and Field Separators . . . . . . . . . . . . . .  11
       3.1.2.  Multiple Values . . . . . . . . . . . . . . . . . . .  11
       3.1.3.  Binary Content  . . . . . . . . . . . . . . . . . . .  11
       3.1.4.  Character Set . . . . . . . . . . . . . . . . . . . .  12
     3.2.  Property Parameters . . . . . . . . . . . . . . . . . . .  12
       3.2.1.  Alternate Text Representation . . . . . . . . . . . .  13
       3.2.2.  Common Name . . . . . . . . . . . . . . . . . . . . .  15
       3.2.3.  Calendar User Type  . . . . . . . . . . . . . . . . .  15
       3.2.4.  Delegators  . . . . . . . . . . . . . . . . . . . . .  16
       3.2.5.  Delegatees  . . . . . . . . . . . . . . . . . . . . .  16
       3.2.6.  Directory Entry Reference . . . . . . . . . . . . . .  17
       3.2.7.  Inline Encoding . . . . . . . . . . . . . . . . . . .  17
       3.2.8.  Format Type . . . . . . . . . . . . . . . . . . . . .  18
       3.2.9.  Free/Busy Time Type . . . . . . . . . . . . . . . . .  19
       3.2.10. Language  . . . . . . . . . . . . . . . . . . . . . .  20
       3.2.11. Group or List Membership  . . . . . . . . . . . . . .  20
       3.2.12. Participation Status  . . . . . . . . . . . . . . . .  21
       3.2.13. Recurrence Identifier Range . . . . . . . . . . . . .  22
       3.2.14. Alarm Trigger Relationship  . . . . . . . . . . . . .  23
       3.2.15. Relationship Type . . . . . . . . . . . . . . . . . .  24
       3.2.16. Participation Role  . . . . . . . . . . . . . . . . .  25
       3.2.17. RSVP Expectation  . . . . . . . . . . . . . . . . . .  25
       3.2.18. Sent By . . . . . . . . . . . . . . . . . . . . . . .  26
       3.2.19. Time Zone Identifier  . . . . . . . . . . . . . . . .  26
       3.2.20. Value Data Types  . . . . . . . . . . . . . . . . . .  28
     3.3.  Property Value Data Types . . . . . . . . . . . . . . . .  29
       3.3.1.  Binary  . . . . . . . . . . . . . . . . . . . . . . .  29
       3.3.2.  Boolean . . . . . . . . . . . . . . . . . . . . . . .  30
       3.3.3.  Calendar User Address . . . . . . . . . . . . . . . .  30
       3.3.4.  Date  . . . . . . . . . . . . . . . . . . . . . . . .  31
       3.3.5.  Date-Time . . . . . . . . . . . . . . . . . . . . . .  31
       3.3.6.  Duration  . . . . . . . . . . . . . . . . . . . . . .  34
       3.3.7.  Float . . . . . . . . . . . . . . . . . . . . . . . .  35
       3.3.8.  Integer . . . . . . . . . . . . . . . . . . . . . . .  35
       3.3.9.  Period of Time  . . . . . . . . . . . . . . . . . . .  36
       3.3.10. Recurrence Rule . . . . . . . . . . . . . . . . . . .  37
       3.3.11. Text  . . . . . . . . . . . . . . . . . . . . . . . .  45



Desruisseaux                Standards Track                     [Page 2]

RFC 5545                       iCalendar                  September 2009


       3.3.12. Time  . . . . . . . . . . . . . . . . . . . . . . . .  46
       3.3.13. URI . . . . . . . . . . . . . . . . . . . . . . . . .  48
       3.3.14. UTC Offset  . . . . . . . . . . . . . . . . . . . . .  49
     3.4.  iCalendar Object  . . . . . . . . . . . . . . . . . . . .  49
     3.5.  Property  . . . . . . . . . . . . . . . . . . . . . . . .  50
     3.6.  Calendar Components . . . . . . . . . . . . . . . . . . .  50
       3.6.1.  Event Component . . . . . . . . . . . . . . . . . . .  52
       3.6.2.  To-Do Component . . . . . . . . . . . . . . . . . . .  56
       3.6.3.  Journal Component . . . . . . . . . . . . . . . . . .  58
       3.6.4.  Free/Busy Component . . . . . . . . . . . . . . . . .  60
       3.6.5.  Time Zone Component . . . . . . . . . . . . . . . . .  63
       3.6.6.  Alarm Component . . . . . . . . . . . . . . . . . . .  72
     3.7.  Calendar Properties . . . . . . . . . . . . . . . . . . .  77
       3.7.1.  Calendar Scale  . . . . . . . . . . . . . . . . . . .  77
       3.7.2.  Method  . . . . . . . . . . . . . . . . . . . . . . .  78
       3.7.3.  Product Identifier  . . . . . . . . . . . . . . . . .  79
       3.7.4.  Version . . . . . . . . . . . . . . . . . . . . . . .  80
     3.8.  Component Properties  . . . . . . . . . . . . . . . . . .  81
       3.8.1.  Descriptive Component Properties  . . . . . . . . . .  81
         3.8.1.1.  Attachment  . . . . . . . . . . . . . . . . . . .  81
         3.8.1.2.  Categories  . . . . . . . . . . . . . . . . . . .  82
         3.8.1.3.  Classification  . . . . . . . . . . . . . . . . .  83
         3.8.1.4.  Comment . . . . . . . . . . . . . . . . . . . . .  84
         3.8.1.5.  Description . . . . . . . . . . . . . . . . . . .  85
         3.8.1.6.  Geographic Position . . . . . . . . . . . . . . .  87
         3.8.1.7.  Location  . . . . . . . . . . . . . . . . . . . .  88
         3.8.1.8.  Percent Complete  . . . . . . . . . . . . . . . .  89
         3.8.1.9.  Priority  . . . . . . . . . . . . . . . . . . . .  90
         3.8.1.10. Resources . . . . . . . . . . . . . . . . . . . .  92
         3.8.1.11. Status  . . . . . . . . . . . . . . . . . . . . .  93
         3.8.1.12. Summary . . . . . . . . . . . . . . . . . . . . .  94
       3.8.2.  Date and Time Component Properties  . . . . . . . . .  95
         3.8.2.1.  Date-Time Completed . . . . . . . . . . . . . . .  95
         3.8.2.2.  Date-Time End . . . . . . . . . . . . . . . . . .  96
         3.8.2.3.  Date-Time Due . . . . . . . . . . . . . . . . . .  97
         3.8.2.4.  Date-Time Start . . . . . . . . . . . . . . . . .  99
         3.8.2.5.  Duration  . . . . . . . . . . . . . . . . . . . . 100
         3.8.2.6.  Free/Busy Time  . . . . . . . . . . . . . . . . . 101
         3.8.2.7.  Time Transparency . . . . . . . . . . . . . . . . 102
       3.8.3.  Time Zone Component Properties  . . . . . . . . . . . 103
         3.8.3.1.  Time Zone Identifier  . . . . . . . . . . . . . . 103
         3.8.3.2.  Time Zone Name  . . . . . . . . . . . . . . . . . 105
         3.8.3.3.  Time Zone Offset From . . . . . . . . . . . . . . 106
         3.8.3.4.  Time Zone Offset To . . . . . . . . . . . . . . . 106
         3.8.3.5.  Time Zone URL . . . . . . . . . . . . . . . . . . 107
       3.8.4.  Relationship Component Properties . . . . . . . . . . 108
         3.8.4.1.  Attendee  . . . . . . . . . . . . . . . . . . . . 108
         3.8.4.2.  Contact . . . . . . . . . . . . . . . . . . . . . 111



Desruisseaux                Standards Track                     [Page 3]

RFC 5545                       iCalendar                  September 2009


         3.8.4.3.  Organizer . . . . . . . . . . . . . . . . . . . . 113
         3.8.4.4.  Recurrence ID . . . . . . . . . . . . . . . . . . 114
         3.8.4.5.  Related To  . . . . . . . . . . . . . . . . . . . 117
         3.8.4.6.  Uniform Resource Locator  . . . . . . . . . . . . 118
         3.8.4.7.  Unique Identifier . . . . . . . . . . . . . . . . 119
       3.8.5.  Recurrence Component Properties . . . . . . . . . . . 120
         3.8.5.1.  Exception Date-Times  . . . . . . . . . . . . . . 120
         3.8.5.2.  Recurrence Date-Times . . . . . . . . . . . . . . 122
         3.8.5.3.  Recurrence Rule . . . . . . . . . . . . . . . . . 124
       3.8.6.  Alarm Component Properties  . . . . . . . . . . . . . 134
         3.8.6.1.  Action  . . . . . . . . . . . . . . . . . . . . . 134
         3.8.6.2.  Repeat Count  . . . . . . . . . . . . . . . . . . 135
         3.8.6.3.  Trigger . . . . . . . . . . . . . . . . . . . . . 135
       3.8.7.  Change Management Component Properties  . . . . . . . 138
         3.8.7.1.  Date-Time Created . . . . . . . . . . . . . . . . 138
         3.8.7.2.  Date-Time Stamp . . . . . . . . . . . . . . . . . 139
         3.8.7.3.  Last Modified . . . . . . . . . . . . . . . . . . 140
         3.8.7.4.  Sequence Number . . . . . . . . . . . . . . . . . 141
       3.8.8.  Miscellaneous Component Properties  . . . . . . . . . 142
         3.8.8.1.  IANA Properties . . . . . . . . . . . . . . . . . 142
         3.8.8.2.  Non-Standard Properties . . . . . . . . . . . . . 142
         3.8.8.3.  Request Status  . . . . . . . . . . . . . . . . . 144
   4.  iCalendar Object Examples . . . . . . . . . . . . . . . . . . 146
   5.  Recommended Practices . . . . . . . . . . . . . . . . . . . . 150
   6.  Internationalization Considerations . . . . . . . . . . . . . 151
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . 151
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 151
     8.1.  iCalendar Media Type Registration . . . . . . . . . . . . 151
     8.2.  New iCalendar Elements Registration . . . . . . . . . . . 155
       8.2.1.  iCalendar Elements Registration Procedure . . . . . . 155
       8.2.2.  Registration Template for Components  . . . . . . . . 155
       8.2.3.  Registration Template for Properties  . . . . . . . . 156
       8.2.4.  Registration Template for Parameters  . . . . . . . . 156
       8.2.5.  Registration Template for Value Data Types  . . . . . 157
       8.2.6.  Registration Template for Values  . . . . . . . . . . 157
     8.3.  Initial iCalendar Elements Registries . . . . . . . . . . 158
       8.3.1.  Components Registry . . . . . . . . . . . . . . . . . 158
       8.3.2.  Properties Registry . . . . . . . . . . . . . . . . . 158
       8.3.3.  Parameters Registry . . . . . . . . . . . . . . . . . 161
       8.3.4.  Value Data Types Registry . . . . . . . . . . . . . . 162
       8.3.5.  Calendar User Types Registry  . . . . . . . . . . . . 162
       8.3.6.  Free/Busy Time Types Registry . . . . . . . . . . . . 163
       8.3.7.  Participation Statuses Registry . . . . . . . . . . . 163
       8.3.8.  Relationship Types Registry . . . . . . . . . . . . . 164
       8.3.9.  Participation Roles Registry  . . . . . . . . . . . . 164
       8.3.10. Actions Registry  . . . . . . . . . . . . . . . . . . 165
       8.3.11. Classifications Registry  . . . . . . . . . . . . . . 165
       8.3.12. Methods Registry  . . . . . . . . . . . . . . . . . . 165



Desruisseaux                Standards Track                     [Page 4]

RFC 5545                       iCalendar                  September 2009


   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 165
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . 166
     10.1. Normative References  . . . . . . . . . . . . . . . . . . 166
     10.2. Informative References  . . . . . . . . . . . . . . . . . 167
   Appendix A.  Differences from RFC 2445  . . . . . . . . . . . . . 169
     A.1.  New Restrictions  . . . . . . . . . . . . . . . . . . . . 169
     A.2.  Restrictions Removed  . . . . . . . . . . . . . . . . . . 169
     A.3.  Deprecated Features . . . . . . . . . . . . . . . . . . . 169

1.  Introduction

   The use of calendaring and scheduling has grown considerably in the
   last decade.  Enterprise and inter-enterprise business has become
   dependent on rapid scheduling of events and actions using this
   information technology.  This memo is intended to progress the level
   of interoperability possible between dissimilar calendaring and
   scheduling applications.  This memo defines a MIME content type for
   exchanging electronic calendaring and scheduling information.  The
   Internet Calendaring and Scheduling Core Object Specification, or
   iCalendar, allows for the capture and exchange of information
   normally stored within a calendaring and scheduling application; such
   as a Personal Information Manager (PIM) or a Group-Scheduling
   product.

   The iCalendar format is suitable as an exchange format between
   applications or systems.  The format is defined in terms of a MIME
   content type.  This will enable the object to be exchanged using
   several transports, including but not limited to SMTP, HTTP, a file
   system, desktop interactive protocols such as the use of a memory-
   based clipboard or drag/drop interactions, point-to-point
   asynchronous communication, wired-network transport, or some form of
   unwired transport such as infrared.

   The memo also provides for the definition of iCalendar object methods
   that will map this content type to a set of messages for supporting
   calendaring and scheduling operations such as requesting, replying
   to, modifying, and canceling meetings or appointments, to-dos, and
   journal entries.  The iCalendar object methods can be used to define
   other calendaring and scheduling operations such as requesting for
   and replying with free/busy time data.  Such a scheduling protocol is
   defined in the iCalendar Transport-independent Interoperability
   Protocol (iTIP) defined in [2446bis].

   The memo also includes a formal grammar for the content type based on
   the Internet ABNF defined in [RFC5234].  This ABNF is required for
   the implementation of parsers and to serve as the definitive
   reference when ambiguities or questions arise in interpreting the
   descriptive prose definition of the memo.  Additional restrictions



Desruisseaux                Standards Track                     [Page 5]

RFC 5545                       iCalendar                  September 2009


   that could not easily be expressed with the ABNF syntax are specified
   as comments in the ABNF.  Comments with normative statements should
   be treated as such.

2.  Basic Grammar and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   This memo makes use of both a descriptive prose and a more formal
   notation for defining the calendaring and scheduling format.

   The notation used in this memo is the ABNF notation of [RFC5234].
   Readers intending on implementing the format defined in this memo
   should be familiar with this notation in order to properly interpret
   the specifications of this memo.

   All numeric values used in this memo are given in decimal notation.

   All names of properties, property parameters, enumerated property
   values, and property parameter values are case-insensitive.  However,
   all other property values are case-sensitive, unless otherwise
   stated.

      Note: All indented editorial notes, such as this one, are intended
      to provide the reader with additional information.  The
      information is not essential to the building of an implementation
      conformant with this memo.  The information is provided to
      highlight a particular feature or characteristic of the memo.

   The format for the iCalendar object is based on the syntax of the
   text/directory media type [RFC2425].  While the iCalendar object is
   not a profile of the text/directory media type [RFC2425], it does
   reuse a number of the elements from the [RFC2425] specification.

2.1.  Formatting Conventions

   The elements defined in this memo are defined in prose.  Many of the
   terms used to describe these have common usage that is different than
   the standards usage of this memo.  In order to reference, within this
   memo, elements of the calendaring and scheduling model, core object
   (this memo), or interoperability protocol [2446bis] some formatting
   conventions have been used.  Calendaring and scheduling roles are
   referred to in quoted-strings of text with the first character of
   each word in uppercase.  For example, "Organizer" refers to a role of
   a "Calendar User" within the scheduling protocol defined by
   [2446bis].  Calendar components defined by this memo are referred to



Desruisseaux                Standards Track                     [Page 6]

RFC 5545                       iCalendar                  September 2009


   with capitalized, quoted-strings of text.  All calendar components
   start with the letter "V".  For example, "VEVENT" refers to the event
   calendar component, "VTODO" refers to the to-do calendar component,
   and "VJOURNAL" refers to the daily journal calendar component.
   Scheduling methods defined by iTIP [2446bis] are referred to with
   capitalized, quoted-strings of text.  For example, "REQUEST" refers
   to the method for requesting a scheduling calendar component be
   created or modified, and "REPLY" refers to the method a recipient of
   a request uses to update their status with the "Organizer" of the
   calendar component.

   The properties defined by this memo are referred to with capitalized,
   quoted-strings of text, followed by the word "property".  For
   example, "ATTENDEE" property refers to the iCalendar property used to
   convey the calendar address of a calendar user.  Property parameters
   defined by this memo are referred to with lowercase, quoted-strings
   of text, followed by the word "parameter".  For example, "value"
   parameter refers to the iCalendar property parameter used to override
   the default value type for a property value.  Enumerated values
   defined by this memo are referred to with capitalized text, either
   alone or followed by the word "value".  For example, the "MINUTELY"
   value can be used with the "FREQ" component of the "RECUR" value type
   to specify repeating components based on an interval of one minute or
   more.

   The following table lists the different characters from the
   [US-ASCII] character set that is referenced in this document.  For
   each character, the table specifies the character name used
   throughout this document, along with its US-ASCII decimal codepoint.






















Desruisseaux                Standards Track                     [Page 7]

RFC 5545                       iCalendar                  September 2009


              +------------------------+-------------------+
              | Character name         | Decimal codepoint |
              +------------------------+-------------------+
              | HTAB                   | 9                 |
              | LF                     | 10                |
              | CR                     | 13                |
              | DQUOTE                 | 22                |
              | SPACE                  | 32                |
              | PLUS SIGN              | 43                |
              | COMMA                  | 44                |
              | HYPHEN-MINUS           | 45                |
              | PERIOD                 | 46                |
              | SOLIDUS                | 47                |
              | COLON                  | 58                |
              | SEMICOLON              | 59                |
              | LATIN CAPITAL LETTER N | 78                |
              | LATIN CAPITAL LETTER T | 84                |
              | LATIN CAPITAL LETTER X | 88                |
              | LATIN CAPITAL LETTER Z | 90                |
              | BACKSLASH              | 92                |
              | LATIN SMALL LETTER N   | 110               |
              +------------------------+-------------------+

2.2.  Related Memos

   Implementers will need to be familiar with several other memos that,
   along with this memo, form a framework for Internet calendaring and
   scheduling standards.  This memo specifies a core specification of
   objects, value types, properties, and property parameters.

   o  iTIP [2446bis] specifies an interoperability protocol for
      scheduling between different implementations;

   o  iCalendar Message-Based Interoperability Protocol (iMIP) [2447bis]
      specifies an Internet email binding for [2446bis].

   This memo does not attempt to repeat the specification of concepts or
   definitions from these other memos.  Where possible, references are
   made to the memo that provides for the specification of these
   concepts or definitions.

3.  iCalendar Object Specification

   The following sections define the details of a Calendaring and
   Scheduling Core Object Specification.  The Calendaring and Scheduling
   Core Object is a collection of calendaring and scheduling
   information.  Typically, this information will consist of an
   iCalendar stream with one or more iCalendar objects.  The body of the



Desruisseaux                Standards Track                     [Page 8]

RFC 5545                       iCalendar                  September 2009


   iCalendar object consists of a sequence of calendar properties and
   one or more calendar components.

   Section 3.1 defines the content line format; Section 3.2 defines the
   property parameter format; Section 3.3 defines the data types for
   property values; Section 3.4 defines the iCalendar object format;
   Section 3.5 defines the iCalendar property format; Section 3.6
   defines the calendar component format; Section 3.7 defines calendar
   properties; and Section 3.8 defines calendar component properties.

   This information is intended to be an integral part of the MIME
   content type registration.  In addition, this information can be used
   independent of such content registration.  In particular, this memo
   has direct applicability for use as a calendaring and scheduling
   exchange format in file-, memory-, or network-based transport
   mechanisms.

3.1.  Content Lines

   The iCalendar object is organized into individual lines of text,
   called content lines.  Content lines are delimited by a line break,
   which is a CRLF sequence (CR character followed by LF character).

   Lines of text SHOULD NOT be longer than 75 octets, excluding the line
   break.  Long content lines SHOULD be split into a multiple line
   representations using a line "folding" technique.  That is, a long
   line can be split between any two characters by inserting a CRLF
   immediately followed by a single linear white-space character (i.e.,
   SPACE or HTAB).  Any sequence of CRLF followed immediately by a
   single linear white-space character is ignored (i.e., removed) when
   processing the content type.

   For example, the line:

     DESCRIPTION:This is a long description that exists on a long line.

   Can be represented as:

     DESCRIPTION:This is a lo
      ng description
       that exists on a long line.

   The process of moving from this folded multiple-line representation
   to its single-line representation is called "unfolding".  Unfolding
   is accomplished by removing the CRLF and the linear white-space
   character that immediately follows.





Desruisseaux                Standards Track                     [Page 9]

RFC 5545                       iCalendar                  September 2009


   When parsing a content line, folded lines MUST first be unfolded
   according to the unfolding procedure described above.

      Note: It is possible for very simple implementations to generate
      improperly folded lines in the middle of a UTF-8 multi-octet
      sequence.  For this reason, implementations need to unfold lines
      in such a way to properly restore the original sequence.

   The content information associated with an iCalendar object is
   formatted using a syntax similar to that defined by [RFC2425].  That
   is, the content information consists of CRLF-separated content lines.

   The following notation defines the lines of content in an iCalendar
   object:

     contentline   = name *(";" param ) ":" value CRLF
     ; This ABNF is just a general definition for an initial parsing
     ; of the content line into its property name, parameter list,
     ; and value string

     ; When parsing a content line, folded lines MUST first
     ; be unfolded according to the unfolding procedure
     ; described above.  When generating a content line, lines
     ; longer than 75 octets SHOULD be folded according to
     ; the folding procedure described above.

     name          = iana-token / x-name

     iana-token    = 1*(ALPHA / DIGIT / "-")
     ; iCalendar identifier registered with IANA

     x-name        = "X-" [vendorid "-"] 1*(ALPHA / DIGIT / "-")
     ; Reserved for experimental use.

     vendorid      = 3*(ALPHA / DIGIT)
     ; Vendor identification

     param         = param-name "=" param-value *("," param-value)
     ; Each property defines the specific ABNF for the parameters
     ; allowed on the property.  Refer to specific properties for
     ; precise parameter ABNF.

     param-name    = iana-token / x-name

     param-value   = paramtext / quoted-string

     paramtext     = *SAFE-CHAR




Desruisseaux                Standards Track                    [Page 10]

RFC 5545                       iCalendar                  September 2009


     value         = *VALUE-CHAR

     quoted-string = DQUOTE *QSAFE-CHAR DQUOTE

     QSAFE-CHAR    = WSP / %x21 / %x23-7E / NON-US-ASCII
     ; Any character except CONTROL and DQUOTE

     SAFE-CHAR     = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E
                   / NON-US-ASCII
     ; Any character except CONTROL, DQUOTE, ";", ":", ","

     VALUE-CHAR    = WSP / %x21-7E / NON-US-ASCII
     ; Any textual character

     NON-US-ASCII  = UTF8-2 / UTF8-3 / UTF8-4
     ; UTF8-2, UTF8-3, and UTF8-4 are defined in [RFC3629]

     CONTROL       = %x00-08 / %x0A-1F / %x7F
     ; All the controls except HTAB

   The property value component of a content line has a format that is
   property specific.  Refer to the section describing each property for
   a definition of this format.

   All names of properties, property parameters, enumerated property
   values and property parameter values are case-insensitive.  However,
   all other property values are case-sensitive, unless otherwise
   stated.

3.1.1.  List and Field Separators

   Some properties and parameters allow a list of values.  Values in a
   list of values MUST be separated by a COMMA character.  There is no
   significance to the order of values in a list.  For those parameter
   values (such as those that specify URI values) that are specified in
   quoted-strings, the individual quoted-strings are separated by a
   COMMA character.

   Some property values are defined in terms of multiple parts.  These
   structured property values MUST have their value parts separated by a
   SEMICOLON character.

   Some properties allow a list of parameters.  Each property parameter
   in a list of property parameters MUST be separated by a SEMICOLON
   character.






Desruisseaux                Standards Track                    [Page 11]

RFC 5545                       iCalendar                  September 2009


   Property parameters with values containing a COLON character, a
   SEMICOLON character or a COMMA character MUST be placed in quoted
   text.

   For example, in the following properties, a SEMICOLON is used to
   separate property parameters from each other and a COMMA character is
   used to separate property values in a value list.

     ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:mailto:
      jsmith@example.com

     RDATE;VALUE=DATE:19970304,19970504,19970704,19970904

3.1.2.  Multiple Values

   Some properties defined in the iCalendar object can have multiple
   values.  The general rule for encoding multi-valued items is to
   simply create a new content line for each value, including the
   property name.  However, it should be noted that some properties
   support encoding multiple values in a single property by separating
   the values with a COMMA character.  Individual property definitions
   should be consulted for determining whether a specific property
   allows multiple values and in which of these two forms.  Multi-valued
   properties MUST NOT be used to specify multiple language variants of
   the same value.  Calendar applications SHOULD display all values.

3.1.3.  Binary Content

   Binary content information in an iCalendar object SHOULD be
   referenced using a URI within a property value.  That is, the binary
   content information SHOULD be placed in an external MIME entity that
   can be referenced by a URI from within the iCalendar object.  In
   applications where this is not feasible, binary content information
   can be included within an iCalendar object, but only after first
   encoding it into text using the "BASE64" encoding method defined in
   [RFC4648].  Inline binary content SHOULD only be used in applications
   whose special circumstances demand that an iCalendar object be
   expressed as a single entity.  A property containing inline binary
   content information MUST specify the "ENCODING" property parameter.
   Binary content information placed external to the iCalendar object
   MUST be referenced by a uniform resource identifier (URI).

   The following example specifies an "ATTACH" property that references
   an attachment external to the iCalendar object with a URI reference:

     ATTACH:http://example.com/public/quarterly-report.doc





Desruisseaux                Standards Track                    [Page 12]

RFC 5545                       iCalendar                  September 2009


   The following example specifies an "ATTACH" property with inline
   binary encoded content information:

     ATTACH;FMTTYPE=text/plain;ENCODING=BASE64;VALUE=BINARY:VGhlIH
      F1aWNrIGJyb3duIGZveCBqdW1wcyBvdmVyIHRoZSBsYXp5IGRvZy4

3.1.4.  Character Set

   There is not a property parameter to declare the charset used in a
   property value.  The default charset for an iCalendar stream is UTF-8
   as defined in [RFC3629].

   The "charset" Content-Type parameter MUST be used in MIME transports
   to specify the charset being used.

3.2.  Property Parameters

   A property can have attributes with which it is associated.  These
   "property parameters" contain meta-information about the property or
   the property value.  Property parameters are provided to specify such
   information as the location of an alternate text representation for a
   property value, the language of a text property value, the value type
   of the property value, and other attributes.

   Property parameter values that contain the COLON, SEMICOLON, or COMMA
   character separators MUST be specified as quoted-string text values.
   Property parameter values MUST NOT contain the DQUOTE character.  The
   DQUOTE character is used as a delimiter for parameter values that
   contain restricted characters or URI text.  For example:

     DESCRIPTION;ALTREP="cid:part1.0001@example.org":The Fall'98 Wild
       Wizards Conference - - Las Vegas\, NV\, USA

   Property parameter values that are not in quoted-strings are case-
   insensitive.

   The general property parameters defined by this memo are defined by
   the following notation:













Desruisseaux                Standards Track                    [Page 13]

RFC 5545                       iCalendar                  September 2009


     icalparameter = altrepparam       ; Alternate text representation
                   / cnparam           ; Common name
                   / cutypeparam       ; Calendar user type
                   / delfromparam      ; Delegator
                   / deltoparam        ; Delegatee
                   / dirparam          ; Directory entry
                   / encodingparam     ; Inline encoding
                   / fmttypeparam      ; Format type
                   / fbtypeparam       ; Free/busy time type
                   / languageparam     ; Language for text
                   / memberparam       ; Group or list membership
                   / partstatparam     ; Participation status
                   / rangeparam        ; Recurrence identifier range
                   / trigrelparam      ; Alarm trigger relationship
                   / reltypeparam      ; Relationship type
                   / roleparam         ; Participation role
                   / rsvpparam         ; RSVP expectation
                   / sentbyparam       ; Sent by
                   / tzidparam         ; Reference to time zone object
                   / valuetypeparam    ; Property value data type
                   / other-param

     other-param   = (iana-param / x-param)

     iana-param  = iana-token "=" param-value *("," param-value)
     ; Some other IANA-registered iCalendar parameter.

     x-param     = x-name "=" param-value *("," param-value)
     ; A non-standard, experimental parameter.

   Applications MUST ignore x-param and iana-param values they don't
   recognize.

3.2.1.  Alternate Text Representation

   Parameter Name:  ALTREP

   Purpose:  To specify an alternate text representation for the
      property value.

   Format Definition:  This property parameter is defined by the
      following notation:

     altrepparam = "ALTREP" "=" DQUOTE uri DQUOTE

   Description:  This parameter specifies a URI that points to an
      alternate representation for a textual property value.  A property
      specifying this parameter MUST also include a value that reflects



Desruisseaux                Standards Track                    [Page 14]

RFC 5545                       iCalendar                  September 2009


      the default representation of the text value.  The URI parameter
      value MUST be specified in a quoted-string.

         Note: While there is no restriction imposed on the URI schemes
         allowed for this parameter, Content Identifier (CID) [RFC2392],
         HTTP [RFC2616], and HTTPS [RFC2818] are the URI schemes most
         commonly used by current implementations.

   Example:

       DESCRIPTION;ALTREP="CID:part3.msg.970415T083000@example.com":
        Project XYZ Review Meeting will include the following agenda
         items: (a) Market Overview\, (b) Finances\, (c) Project Man
        agement

      The "ALTREP" property parameter value might point to a "text/html"
      content portion.

       Content-Type:text/html
       Content-Id:<part3.msg.970415T083000@example.com>

       <html>
         <head>
          <title></title>
         </head>
         <body>
           <p>
             <b>Project XYZ Review Meeting</b> will include
             the following agenda items:
             <ol>
               <li>Market Overview</li>
               <li>Finances</li>
               <li>Project Management</li>
             </ol>
           </p>
         </body>
       </html>

3.2.2.  Common Name

   Parameter Name:  CN

   Purpose:  To specify the common name to be associated with the
      calendar user specified by the property.

   Format Definition:  This property parameter is defined by the
      following notation:




Desruisseaux                Standards Track                    [Page 15]

RFC 5545                       iCalendar                  September 2009


     cnparam    = "CN" "=" param-value

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter specifies the common name
      to be associated with the calendar user specified by the property.
      The parameter value is text.  The parameter value can be used for
      display text to be associated with the calendar address specified
      by the property.

   Example:

       ORGANIZER;CN="John Smith":mailto:jsmith@example.com

3.2.3.  Calendar User Type

   Parameter Name:  CUTYPE

   Purpose:  To identify the type of calendar user specified by the
      property.

   Format Definition:  This property parameter is defined by the
      following notation:

       cutypeparam        = "CUTYPE" "="
                          ("INDIVIDUAL"   ; An individual
                         / "GROUP"        ; A group of individuals
                         / "RESOURCE"     ; A physical resource
                         / "ROOM"         ; A room resource
                         / "UNKNOWN"      ; Otherwise not known
                         / x-name         ; Experimental type
                         / iana-token)    ; Other IANA-registered
                                          ; type
       ; Default is INDIVIDUAL

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter identifies the type of
      calendar user specified by the property.  If not specified on a
      property that allows this parameter, the default is INDIVIDUAL.
      Applications MUST treat x-name and iana-token values they don't
      recognize the same way as they would the UNKNOWN value.

   Example:

       ATTENDEE;CUTYPE=GROUP:mailto:ietf-calsch@example.org







Desruisseaux                Standards Track                    [Page 16]

RFC 5545                       iCalendar                  September 2009


3.2.4.  Delegators

   Parameter Name:  DELEGATED-FROM

   Purpose:  To specify the calendar users that have delegated their
      participation to the calendar user specified by the property.

   Format Definition:  This property parameter is defined by the
      following notation:

       delfromparam       = "DELEGATED-FROM" "=" DQUOTE cal-address
                             DQUOTE *("," DQUOTE cal-address DQUOTE)

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  This parameter specifies those calendar
      users that have delegated their participation in a group-scheduled
      event or to-do to the calendar user specified by the property.
      The individual calendar address parameter values MUST each be
      specified in a quoted-string.

   Example:

       ATTENDEE;DELEGATED-FROM="mailto:jsmith@example.com":mailto:
        jdoe@example.com

3.2.5.  Delegatees

   Parameter Name:  DELEGATED-TO

   Purpose:  To specify the calendar users to whom the calendar user
      specified by the property has delegated participation.

   Format Definition:  This property parameter is defined by the
      following notation:

       deltoparam = "DELEGATED-TO" "=" DQUOTE cal-address DQUOTE
                    *("," DQUOTE cal-address DQUOTE)

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  This parameter specifies those calendar
      users whom have been delegated participation in a group-scheduled
      event or to-do by the calendar user specified by the property.
      The individual calendar address parameter values MUST each be
      specified in a quoted-string.







Desruisseaux                Standards Track                    [Page 17]

RFC 5545                       iCalendar                  September 2009


   Example:

       ATTENDEE;DELEGATED-TO="mailto:jdoe@example.com","mailto:jqpublic
        @example.com":mailto:jsmith@example.com

3.2.6.  Directory Entry Reference

   Parameter Name:  DIR

   Purpose:  To specify reference to a directory entry associated with
      the calendar user specified by the property.

   Format Definition:  This property parameter is defined by the
      following notation:

       dirparam   = "DIR" "=" DQUOTE uri DQUOTE

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter specifies a reference to
      the directory entry associated with the calendar user specified by
      the property.  The parameter value is a URI.  The URI parameter
      value MUST be specified in a quoted-string.

         Note: While there is no restriction imposed on the URI schemes
         allowed for this parameter, CID [RFC2392], DATA [RFC2397], FILE
         [RFC1738], FTP [RFC1738], HTTP [RFC2616], HTTPS [RFC2818], LDAP
         [RFC4516], and MID [RFC2392] are the URI schemes most commonly
         used by current implementations.

   Example:

       ORGANIZER;DIR="ldap://example.com:6666/o=ABC%20Industries,
        c=US???(cn=Jim%20Dolittle)":mailto:jimdo@example.com

3.2.7.  Inline Encoding

   Parameter Name:  ENCODING

   Purpose:  To specify an alternate inline encoding for the property
      value.

   Format Definition:  This property parameter is defined by the
      following notation:








Desruisseaux                Standards Track                    [Page 18]

RFC 5545                       iCalendar                  September 2009


       encodingparam      = "ENCODING" "="
                          ( "8BIT"
          ; "8bit" text encoding is defined in [RFC2045]
                          / "BASE64"
          ; "BASE64" binary encoding format is defined in [RFC4648]
                          )

   Description:  This property parameter identifies the inline encoding
      used in a property value.  The default encoding is "8BIT",
      corresponding to a property value consisting of text.  The
      "BASE64" encoding type corresponds to a property value encoded
      using the "BASE64" encoding defined in [RFC2045].

      If the value type parameter is ";VALUE=BINARY", then the inline
      encoding parameter MUST be specified with the value
      ";ENCODING=BASE64".

   Example:

     ATTACH;FMTTYPE=text/plain;ENCODING=BASE64;VALUE=BINARY:TG9yZW
      0gaXBzdW0gZG9sb3Igc2l0IGFtZXQsIGNvbnNlY3RldHVyIGFkaXBpc2ljaW
      5nIGVsaXQsIHNlZCBkbyBlaXVzbW9kIHRlbXBvciBpbmNpZGlkdW50IHV0IG
      xhYm9yZSBldCBkb2xvcmUgbWFnbmEgYWxpcXVhLiBVdCBlbmltIGFkIG1pbm
      ltIHZlbmlhbSwgcXVpcyBub3N0cnVkIGV4ZXJjaXRhdGlvbiB1bGxhbWNvIG
      xhYm9yaXMgbmlzaSB1dCBhbGlxdWlwIGV4IGVhIGNvbW1vZG8gY29uc2VxdW
      F0LiBEdWlzIGF1dGUgaXJ1cmUgZG9sb3IgaW4gcmVwcmVoZW5kZXJpdCBpbi
      B2b2x1cHRhdGUgdmVsaXQgZXNzZSBjaWxsdW0gZG9sb3JlIGV1IGZ1Z2lhdC
      BudWxsYSBwYXJpYXR1ci4gRXhjZXB0ZXVyIHNpbnQgb2NjYWVjYXQgY3VwaW
      RhdGF0IG5vbiBwcm9pZGVudCwgc3VudCBpbiBjdWxwYSBxdWkgb2ZmaWNpYS
      BkZXNlcnVudCBtb2xsaXQgYW5pbSBpZCBlc3QgbGFib3J1bS4=

3.2.8.  Format Type

   Parameter Name:  FMTTYPE

   Purpose:  To specify the content type of a referenced object.

   Format Definition:  This property parameter is defined by the
      following notation:

       fmttypeparam = "FMTTYPE" "=" type-name "/" subtype-name
                      ; Where "type-name" and "subtype-name" are
                      ; defined in Section 4.2 of [RFC4288].

   Description:  This parameter can be specified on properties that are
      used to reference an object.  The parameter specifies the media
      type [RFC4288] of the referenced object.  For example, on the
      "ATTACH" property, an FTP type URI value does not, by itself,



Desruisseaux                Standards Track                    [Page 19]

RFC 5545                       iCalendar                  September 2009


      necessarily convey the type of content associated with the
      resource.  The parameter value MUST be the text for either an
      IANA-registered media type or a non-standard media type.

   Example:

       ATTACH;FMTTYPE=application/msword:ftp://example.com/pub/docs/
        agenda.doc

3.2.9.  Free/Busy Time Type

   Parameter Name:  FBTYPE

   Purpose:  To specify the free or busy time type.

   Format Definition:  This property parameter is defined by the
      following notation:

       fbtypeparam        = "FBTYPE" "=" ("FREE" / "BUSY"
                          / "BUSY-UNAVAILABLE" / "BUSY-TENTATIVE"
                          / x-name
                ; Some experimental iCalendar free/busy type.
                          / iana-token)
                ; Some other IANA-registered iCalendar free/busy type.

   Description:  This parameter specifies the free or busy time type.
      The value FREE indicates that the time interval is free for
      scheduling.  The value BUSY indicates that the time interval is
      busy because one or more events have been scheduled for that
      interval.  The value BUSY-UNAVAILABLE indicates that the time
      interval is busy and that the interval can not be scheduled.  The
      value BUSY-TENTATIVE indicates that the time interval is busy
      because one or more events have been tentatively scheduled for
      that interval.  If not specified on a property that allows this
      parameter, the default is BUSY.  Applications MUST treat x-name
      and iana-token values they don't recognize the same way as they
      would the BUSY value.

   Example:  The following is an example of this parameter on a
      "FREEBUSY" property.

       FREEBUSY;FBTYPE=BUSY:19980415T133000Z/19980415T170000Z









Desruisseaux                Standards Track                    [Page 20]

RFC 5545                       iCalendar                  September 2009


3.2.10.  Language

   Parameter Name:  LANGUAGE

   Purpose:  To specify the language for text values in a property or
      property parameter.

   Format Definition:  This property parameter is defined by the
      following notation:

       languageparam = "LANGUAGE" "=" language

       language = Language-Tag
                  ; As defined in [RFC5646].

   Description:  This parameter identifies the language of the text in
      the property value and of all property parameter values of the
      property.  The value of the "LANGUAGE" property parameter is that
      defined in [RFC5646].

      For transport in a MIME entity, the Content-Language header field
      can be used to set the default language for the entire body part.
      Otherwise, no default language is assumed.

   Example:  The following are examples of this parameter on the
      "SUMMARY" and "LOCATION" properties:

       SUMMARY;LANGUAGE=en-US:Company Holiday Party

       LOCATION;LANGUAGE=en:Germany

       LOCATION;LANGUAGE=no:Tyskland

3.2.11.  Group or List Membership

   Parameter Name:  MEMBER

   Purpose:  To specify the group or list membership of the calendar
      user specified by the property.

   Format Definition:  This property parameter is defined by the
      following notation:

       memberparam        = "MEMBER" "=" DQUOTE cal-address DQUOTE
                            *("," DQUOTE cal-address DQUOTE)






Desruisseaux                Standards Track                    [Page 21]

RFC 5545                       iCalendar                  September 2009


   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter identifies the groups or
      list membership for the calendar user specified by the property.
      The parameter value is either a single calendar address in a
      quoted-string or a COMMA-separated list of calendar addresses,
      each in a quoted-string.  The individual calendar address
      parameter values MUST each be specified in a quoted-string.

   Example:

       ATTENDEE;MEMBER="mailto:ietf-calsch@example.org":mailto:
        jsmith@example.com

       ATTENDEE;MEMBER="mailto:projectA@example.com","mailto:pr
        ojectB@example.com":mailto:janedoe@example.com

3.2.12.  Participation Status

   Parameter Name:  PARTSTAT

   Purpose:  To specify the participation status for the calendar user
      specified by the property.

   Format Definition:  This property parameter is defined by the
      following notation:

       partstatparam    = "PARTSTAT" "="
                         (partstat-event
                        / partstat-todo
                        / partstat-jour)

       partstat-event   = ("NEEDS-ACTION"    ; Event needs action
                        / "ACCEPTED"         ; Event accepted
                        / "DECLINED"         ; Event declined
                        / "TENTATIVE"        ; Event tentatively
                                             ; accepted
                        / "DELEGATED"        ; Event delegated
                        / x-name             ; Experimental status
                        / iana-token)        ; Other IANA-registered
                                             ; status
       ; These are the participation statuses for a "VEVENT".
       ; Default is NEEDS-ACTION.

       partstat-todo    = ("NEEDS-ACTION"    ; To-do needs action
                        / "ACCEPTED"         ; To-do accepted
                        / "DECLINED"         ; To-do declined
                        / "TENTATIVE"        ; To-do tentatively
                                             ; accepted



Desruisseaux                Standards Track                    [Page 22]

RFC 5545                       iCalendar                  September 2009


                        / "DELEGATED"        ; To-do delegated
                        / "COMPLETED"        ; To-do completed
                                             ; COMPLETED property has
                                             ; DATE-TIME completed
                        / "IN-PROCESS"       ; To-do in process of
                                             ; being completed
                        / x-name             ; Experimental status
                        / iana-token)        ; Other IANA-registered
                                             ; status
       ; These are the participation statuses for a "VTODO".
       ; Default is NEEDS-ACTION.



       partstat-jour    = ("NEEDS-ACTION"    ; Journal needs action
                        / "ACCEPTED"         ; Journal accepted
                        / "DECLINED"         ; Journal declined
                        / x-name             ; Experimental status
                        / iana-token)        ; Other IANA-registered
                                             ; status
       ; These are the participation statuses for a "VJOURNAL".
       ; Default is NEEDS-ACTION.

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter identifies the
      participation status for the calendar user specified by the
      property value.  The parameter values differ depending on whether
      they are associated with a group-scheduled "VEVENT", "VTODO", or
      "VJOURNAL".  The values MUST match one of the values allowed for
      the given calendar component.  If not specified on a property that
      allows this parameter, the default value is NEEDS-ACTION.
      Applications MUST treat x-name and iana-token values they don't
      recognize the same way as they would the NEEDS-ACTION value.

   Example:

       ATTENDEE;PARTSTAT=DECLINED:mailto:jsmith@example.com

3.2.13.  Recurrence Identifier Range

   Parameter Name:  RANGE

   Purpose:  To specify the effective range of recurrence instances from
      the instance specified by the recurrence identifier specified by
      the property.

   Format Definition:  This property parameter is defined by the
      following notation:



Desruisseaux                Standards Track                    [Page 23]

RFC 5545                       iCalendar                  September 2009


       rangeparam = "RANGE" "=" "THISANDFUTURE"
       ; To specify the instance specified by the recurrence identifier
       ; and all subsequent recurrence instances.

   Description:  This parameter can be specified on a property that
      specifies a recurrence identifier.  The parameter specifies the
      effective range of recurrence instances that is specified by the
      property.  The effective range is from the recurrence identifier
      specified by the property.  If this parameter is not specified on
      an allowed property, then the default range is the single instance
      specified by the recurrence identifier value of the property.  The
      parameter value can only be "THISANDFUTURE" to indicate a range
      defined by the recurrence identifier and all subsequent instances.
      The value "THISANDPRIOR" is deprecated by this revision of
      iCalendar and MUST NOT be generated by applications.

   Example:

       RECURRENCE-ID;RANGE=THISANDFUTURE:19980401T133000Z

3.2.14.  Alarm Trigger Relationship

   Parameter Name:  RELATED

   Purpose:  To specify the relationship of the alarm trigger with
      respect to the start or end of the calendar component.

   Format Definition:  This property parameter is defined by the
      following notation:

       trigrelparam       = "RELATED" "="
                           ("START"       ; Trigger off of start
                          / "END")        ; Trigger off of end

   Description:  This parameter can be specified on properties that
      specify an alarm trigger with a "DURATION" value type.  The
      parameter specifies whether the alarm will trigger relative to the
      start or end of the calendar component.  The parameter value START
      will set the alarm to trigger off the start of the calendar
      component; the parameter value END will set the alarm to trigger
      off the end of the calendar component.  If the parameter is not
      specified on an allowable property, then the default is START.

   Example:

       TRIGGER;RELATED=END:PT5M





Desruisseaux                Standards Track                    [Page 24]

RFC 5545                       iCalendar                  September 2009


3.2.15.  Relationship Type

   Parameter Name:  RELTYPE

   Purpose:  To specify the type of hierarchical relationship associated
      with the calendar component specified by the property.

   Format Definition:  This property parameter is defined by the
      following notation:

       reltypeparam       = "RELTYPE" "="
                           ("PARENT"    ; Parent relationship - Default
                          / "CHILD"     ; Child relationship
                          / "SIBLING"   ; Sibling relationship
                          / iana-token  ; Some other IANA-registered
                                        ; iCalendar relationship type
                          / x-name)     ; A non-standard, experimental
                                        ; relationship type

   Description:  This parameter can be specified on a property that
      references another related calendar.  The parameter specifies the
      hierarchical relationship type of the calendar component
      referenced by the property.  The parameter value can be PARENT, to
      indicate that the referenced calendar component is a superior of
      calendar component; CHILD to indicate that the referenced calendar
      component is a subordinate of the calendar component; or SIBLING
      to indicate that the referenced calendar component is a peer of
      the calendar component.  If this parameter is not specified on an
      allowable property, the default relationship type is PARENT.
      Applications MUST treat x-name and iana-token values they don't
      recognize the same way as they would the PARENT value.

   Example:

       RELATED-TO;RELTYPE=SIBLING:19960401-080045-4000F192713@
        example.com

3.2.16.  Participation Role

   Parameter Name:  ROLE

   Purpose:  To specify the participation role for the calendar user
      specified by the property.

   Format Definition:  This property parameter is defined by the
      following notation:





Desruisseaux                Standards Track                    [Page 25]

RFC 5545                       iCalendar                  September 2009


       roleparam  = "ROLE" "="
                   ("CHAIR"             ; Indicates chair of the
                                        ; calendar entity
                  / "REQ-PARTICIPANT"   ; Indicates a participant whose
                                        ; participation is required
                  / "OPT-PARTICIPANT"   ; Indicates a participant whose
                                        ; participation is optional
                  / "NON-PARTICIPANT"   ; Indicates a participant who
                                        ; is copied for information
                                        ; purposes only
                  / x-name              ; Experimental role
                  / iana-token)         ; Other IANA role
       ; Default is REQ-PARTICIPANT

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter specifies the participation
      role for the calendar user specified by the property in the group
      schedule calendar component.  If not specified on a property that
      allows this parameter, the default value is REQ-PARTICIPANT.
      Applications MUST treat x-name and iana-token values they don't
      recognize the same way as they would the REQ-PARTICIPANT value.

   Example:

       ATTENDEE;ROLE=CHAIR:mailto:mrbig@example.com

3.2.17.  RSVP Expectation

   Parameter Name:  RSVP

   Purpose:  To specify whether there is an expectation of a favor of a
      reply from the calendar user specified by the property value.

   Format Definition:  This property parameter is defined by the
      following notation:

       rsvpparam = "RSVP" "=" ("TRUE" / "FALSE")
       ; Default is FALSE

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter identifies the expectation
      of a reply from the calendar user specified by the property value.
      This parameter is used by the "Organizer" to request a
      participation status reply from an "Attendee" of a group-scheduled
      event or to-do.  If not specified on a property that allows this
      parameter, the default value is FALSE.





Desruisseaux                Standards Track                    [Page 26]

RFC 5545                       iCalendar                  September 2009


   Example:

       ATTENDEE;RSVP=TRUE:mailto:jsmith@example.com

3.2.18.  Sent By

   Parameter Name:  SENT-BY

   Purpose:  To specify the calendar user that is acting on behalf of
      the calendar user specified by the property.

   Format Definition:  This property parameter is defined by the
      following notation:

       sentbyparam        = "SENT-BY" "=" DQUOTE cal-address DQUOTE

   Description:  This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter specifies the calendar user
      that is acting on behalf of the calendar user specified by the
      property.  The parameter value MUST be a mailto URI as defined in
      [RFC2368].  The individual calendar address parameter values MUST
      each be specified in a quoted-string.

   Example:

       ORGANIZER;SENT-BY="mailto:sray@example.com":mailto:
        jsmith@example.com

3.2.19.  Time Zone Identifier

   Parameter Name:  TZID

   Purpose:  To specify the identifier for the time zone definition for
      a time component in the property value.

   Format Definition:  This property parameter is defined by the
      following notation:

       tzidparam  = "TZID" "=" [tzidprefix] paramtext

       tzidprefix = "/"

   Description:  This parameter MUST be specified on the "DTSTART",
      "DTEND", "DUE", "EXDATE", and "RDATE" properties when either a
      DATE-TIME or TIME value type is specified and when the value is
      neither a UTC or a "floating" time.  Refer to the DATE-TIME or
      TIME value type definition for a description of UTC and "floating
      time" formats.  This property parameter specifies a text value



Desruisseaux                Standards Track                    [Page 27]

RFC 5545                       iCalendar                  September 2009


      that uniquely identifies the "VTIMEZONE" calendar component to be
      used when evaluating the time portion of the property.  The value
      of the "TZID" property parameter will be equal to the value of the
      "TZID" property for the matching time zone definition.  An
      individual "VTIMEZONE" calendar component MUST be specified for
      each unique "TZID" parameter value specified in the iCalendar
      object.

      The parameter MUST be specified on properties with a DATE-TIME
      value if the DATE-TIME is not either a UTC or a "floating" time.
      Failure to include and follow VTIMEZONE definitions in iCalendar
      objects may lead to inconsistent understanding of the local time
      at any given location.

      The presence of the SOLIDUS character as a prefix, indicates that
      this "TZID" represents a unique ID in a globally defined time zone
      registry (when such registry is defined).

         Note: This document does not define a naming convention for
         time zone identifiers.  Implementers may want to use the naming
         conventions defined in existing time zone specifications such
         as the public-domain TZ database [TZDB].  The specification of
         globally unique time zone identifiers is not addressed by this
         document and is left for future study.

      The following are examples of this property parameter:

       DTSTART;TZID=America/New_York:19980119T020000

       DTEND;TZID=America/New_York:19980119T030000

      The "TZID" property parameter MUST NOT be applied to DATE
      properties and DATE-TIME or TIME properties whose time values are
      specified in UTC.

      The use of local time in a DATE-TIME or TIME value without the
      "TZID" property parameter is to be interpreted as floating time,
      regardless of the existence of "VTIMEZONE" calendar components in
      the iCalendar object.

      For more information, see the sections on the value types DATE-
      TIME and TIME.









Desruisseaux                Standards Track                    [Page 28]

RFC 5545                       iCalendar                  September 2009


3.2.20.  Value Data Types

   Parameter Name:  VALUE

   Purpose:  To explicitly specify the value type format for a property
      value.

   Format Definition:  This property parameter is defined by the
      following notation:

       valuetypeparam = "VALUE" "=" valuetype

       valuetype  = ("BINARY"
                  / "BOOLEAN"
                  / "CAL-ADDRESS"
                  / "DATE"
                  / "DATE-TIME"
                  / "DURATION"
                  / "FLOAT"
                  / "INTEGER"
                  / "PERIOD"
                  / "RECUR"
                  / "TEXT"
                  / "TIME"
                  / "URI"
                  / "UTC-OFFSET"
                  / x-name
                  ; Some experimental iCalendar value type.
                  / iana-token)
                  ; Some other IANA-registered iCalendar value type.

   Description:  This parameter specifies the value type and format of
      the property value.  The property values MUST be of a single value
      type.  For example, a "RDATE" property cannot have a combination
      of DATE-TIME and TIME value types.

      If the property's value is the default value type, then this
      parameter need not be specified.  However, if the property's
      default value type is overridden by some other allowable value
      type, then this parameter MUST be specified.

      Applications MUST preserve the value data for x-name and iana-
      token values that they don't recognize without attempting to
      interpret or parse the value data.







Desruisseaux                Standards Track                    [Page 29]

RFC 5545                       iCalendar                  September 2009


3.3.  Property Value Data Types

   The properties in an iCalendar object are strongly typed.  The
   definition of each property restricts the value to be one of the
   value data types, or simply value types, defined in this section.
   The value type for a property will either be specified implicitly as
   the default value type or will be explicitly specified with the
   "VALUE" parameter.  If the value type of a property is one of the
   alternate valid types, then it MUST be explicitly specified with the
   "VALUE" parameter.

3.3.1.  Binary

   Value Name:  BINARY

   Purpose:  This value type is used to identify properties that contain
      a character encoding of inline binary data.  For example, an
      inline attachment of a document might be included in an iCalendar
      object.

   Format Definition:  This value type is defined by the following
      notation:

       binary     = *(4b-char) [b-end]
       ; A "BASE64" encoded character string, as defined by [RFC4648].

       b-end      = (2b-char "==") / (3b-char "=")

       b-char = ALPHA / DIGIT / "+" / "/"

   Description:  Property values with this value type MUST also include
      the inline encoding parameter sequence of ";ENCODING=BASE64".
      That is, all inline binary data MUST first be character encoded
      using the "BASE64" encoding method defined in [RFC2045].  No
      additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) is defined for this value type.















Desruisseaux                Standards Track                    [Page 30]

RFC 5545                       iCalendar                  September 2009


   Example:  The following is an example of a "BASE64" encoded binary
      value data:

     ATTACH;FMTTYPE=image/vnd.microsoft.icon;ENCODING=BASE64;VALUE
      =BINARY:AAABAAEAEBAQAAEABAAoAQAAFgAAACgAAAAQAAAAIAAAAAEABAAA
      AAAAAAAAAAAAAAAAAAAAAAAAAAAAAACAAAAAgIAAAICAgADAwMAA////AAAA
      AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
      AAAAAAAAAAAAAAAAAAAAAAMwAAAAAAABNEMQAAAAAAAkQgAAAAAAJEREQgAA
      ACECQ0QgEgAAQxQzM0E0AABERCRCREQAADRDJEJEQwAAAhA0QwEQAAAAAERE
      AAAAAAAAREQAAAAAAAAkQgAAAAAAAAMgAAAAAAAAAAAAAAAAAAAAAAAAAAAA
      AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
      AAAAAAAAAAAA

3.3.2.  Boolean

   Value Name:  BOOLEAN

   Purpose:  This value type is used to identify properties that contain
      either a "TRUE" or "FALSE" Boolean value.

   Format Definition:  This value type is defined by the following
      notation:

       boolean    = "TRUE" / "FALSE"

   Description:  These values are case-insensitive text.  No additional
      content value encoding (i.e., BACKSLASH character encoding, see
      Section 3.3.11) is defined for this value type.

   Example:  The following is an example of a hypothetical property that
      has a BOOLEAN value type:

       TRUE

3.3.3.  Calendar User Address

   Value Name:  CAL-ADDRESS

   Purpose:  This value type is used to identify properties that contain
      a calendar user address.

   Format Definition:  This value type is defined by the following
      notation:

       cal-address        = uri

   Description:  The value is a URI as defined by [RFC3986] or any other
      IANA-registered form for a URI.  When used to address an Internet



Desruisseaux                Standards Track                    [Page 31]

RFC 5545                       iCalendar                  September 2009


      email transport address for a calendar user, the value MUST be a
      mailto URI, as defined by [RFC2368].  No additional content value
      encoding (i.e., BACKSLASH character encoding, see Section 3.3.11)
      is defined for this value type.

   Example:

    mailto:jane_doe@example.com

3.3.4.  Date

   Value Name:  DATE

   Purpose:  This value type is used to identify values that contain a
      calendar date.

   Format Definition:  This value type is defined by the following
      notation:

       date               = date-value

       date-value         = date-fullyear date-month date-mday
       date-fullyear      = 4DIGIT
       date-month         = 2DIGIT        ;01-12
       date-mday          = 2DIGIT        ;01-28, 01-29, 01-30, 01-31
                                          ;based on month/year

   Description:  If the property permits, multiple "date" values are
      specified as a COMMA-separated list of values.  The format for the
      value type is based on the [ISO.8601.2004] complete
      representation, basic format for a calendar date.  The textual
      format specifies a four-digit year, two-digit month, and two-digit
      day of the month.  There are no separator characters between the
      year, month, and day component text.

      No additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) is defined for this value type.

   Example:  The following represents July 14, 1997:

       19970714

3.3.5.  Date-Time

   Value Name:  DATE-TIME

   Purpose:  This value type is used to identify values that specify a
      precise calendar date and time of day.



Desruisseaux                Standards Track                    [Page 32]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This value type is defined by the following
      notation:

       date-time  = date "T" time ;As specified in the DATE and TIME
                                  ;value definitions

   Description:  If the property permits, multiple "DATE-TIME" values
      are specified as a COMMA-separated list of values.  No additional
      content value encoding (i.e., BACKSLASH character encoding, see
      Section 3.3.11) is defined for this value type.

      The "DATE-TIME" value type is used to identify values that contain
      a precise calendar date and time of day.  The format is based on
      the [ISO.8601.2004] complete representation, basic format for a
      calendar date and time of day.  The text format is a concatenation
      of the "date", followed by the LATIN CAPITAL LETTER T character,
      the time designator, followed by the "time" format.

      The "DATE-TIME" value type expresses time values in three forms:

      The form of date and time with UTC offset MUST NOT be used.  For
      example, the following is not valid for a DATE-TIME value:

       19980119T230000-0800       ;Invalid time format

      FORM #1: DATE WITH LOCAL TIME

      The date with local time form is simply a DATE-TIME value that
      does not contain the UTC designator nor does it reference a time
      zone.  For example, the following represents January 18, 1998, at
      11 PM:

       19980118T230000

      DATE-TIME values of this type are said to be "floating" and are
      not bound to any time zone in particular.  They are used to
      represent the same hour, minute, and second value regardless of
      which time zone is currently being observed.  For example, an
      event can be defined that indicates that an individual will be
      busy from 11:00 AM to 1:00 PM every day, no matter which time zone
      the person is in.  In these cases, a local time can be specified.
      The recipient of an iCalendar object with a property value
      consisting of a local time, without any relative time zone
      information, SHOULD interpret the value as being fixed to whatever
      time zone the "ATTENDEE" is in at any given moment.  This means
      that two "Attendees", in different time zones, receiving the same
      event definition as a floating time, may be participating in the




Desruisseaux                Standards Track                    [Page 33]

RFC 5545                       iCalendar                  September 2009


      event at different actual times.  Floating time SHOULD only be
      used where that is the reasonable behavior.

      In most cases, a fixed time is desired.  To properly communicate a
      fixed time in a property value, either UTC time or local time with
      time zone reference MUST be specified.

      The use of local time in a DATE-TIME value without the "TZID"
      property parameter is to be interpreted as floating time,
      regardless of the existence of "VTIMEZONE" calendar components in
      the iCalendar object.

      FORM #2: DATE WITH UTC TIME

      The date with UTC time, or absolute time, is identified by a LATIN
      CAPITAL LETTER Z suffix character, the UTC designator, appended to
      the time value.  For example, the following represents January 19,
      1998, at 0700 UTC:

       19980119T070000Z

      The "TZID" property parameter MUST NOT be applied to DATE-TIME
      properties whose time values are specified in UTC.

      FORM #3: DATE WITH LOCAL TIME AND TIME ZONE REFERENCE

      The date and local time with reference to time zone information is
      identified by the use the "TZID" property parameter to reference
      the appropriate time zone definition.  "TZID" is discussed in
      detail in Section 3.2.19.  For example, the following represents
      2:00 A.M. in New York on January 19, 1998:

       TZID=America/New_York:19980119T020000

      If, based on the definition of the referenced time zone, the local
      time described occurs more than once (when changing from daylight
      to standard time), the DATE-TIME value refers to the first
      occurrence of the referenced time.  Thus, TZID=America/
      New_York:20071104T013000 indicates November 4, 2007 at 1:30 A.M.
      EDT (UTC-04:00).  If the local time described does not occur (when
      changing from standard to daylight time), the DATE-TIME value is
      interpreted using the UTC offset before the gap in local times.
      Thus, TZID=America/New_York:20070311T023000 indicates March 11,
      2007 at 3:30 A.M. EDT (UTC-04:00), one hour after 1:30 A.M. EST
      (UTC-05:00).






Desruisseaux                Standards Track                    [Page 34]

RFC 5545                       iCalendar                  September 2009


      A time value MUST only specify the second 60 when specifying a
      positive leap second.  For example:

       19970630T235960Z

      Implementations that do not support leap seconds SHOULD interpret
      the second 60 as equivalent to the second 59.

   Example:  The following represents July 14, 1997, at 1:30 PM in New
      York City in each of the three time formats, using the "DTSTART"
      property.

       DTSTART:19970714T133000                   ; Local time
       DTSTART:19970714T173000Z                  ; UTC time
       DTSTART;TZID=America/New_York:19970714T133000
                                                 ; Local time and time
                                                 ; zone reference

3.3.6.  Duration

   Value Name:  DURATION

   Purpose:  This value type is used to identify properties that contain
      a duration of time.

   Format Definition:  This value type is defined by the following
      notation:

       dur-value  = (["+"] / "-") "P" (dur-date / dur-time / dur-week)

       dur-date   = dur-day [dur-time]
       dur-time   = "T" (dur-hour / dur-minute / dur-second)
       dur-week   = 1*DIGIT "W"
       dur-hour   = 1*DIGIT "H" [dur-minute]
       dur-minute = 1*DIGIT "M" [dur-second]
       dur-second = 1*DIGIT "S"
       dur-day    = 1*DIGIT "D"

   Description:  If the property permits, multiple "duration" values are
      specified by a COMMA-separated list of values.  The format is
      based on the [ISO.8601.2004] complete representation basic format
      with designators for the duration of time.  The format can
      represent nominal durations (weeks and days) and accurate
      durations (hours, minutes, and seconds).  Note that unlike
      [ISO.8601.2004], this value type doesn't support the "Y" and "M"
      designators to specify durations in terms of years and months.





Desruisseaux                Standards Track                    [Page 35]

RFC 5545                       iCalendar                  September 2009


      The duration of a week or a day depends on its position in the
      calendar.  In the case of discontinuities in the time scale, such
      as the change from standard time to daylight time and back, the
      computation of the exact duration requires the subtraction or
      addition of the change of duration of the discontinuity.  Leap
      seconds MUST NOT be considered when computing an exact duration.
      When computing an exact duration, the greatest order time
      components MUST be added first, that is, the number of days MUST
      be added first, followed by the number of hours, number of
      minutes, and number of seconds.

      Negative durations are typically used to schedule an alarm to
      trigger before an associated time (see Section 3.8.6.3).

      No additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) are defined for this value type.

   Example:  A duration of 15 days, 5 hours, and 20 seconds would be:

       P15DT5H0M20S

      A duration of 7 weeks would be:

       P7W

3.3.7.  Float

   Value Name:  FLOAT

   Purpose:  This value type is used to identify properties that contain
      a real-number value.

   Format Definition:  This value type is defined by the following
      notation:

       float      = (["+"] / "-") 1*DIGIT ["." 1*DIGIT]

   Description:  If the property permits, multiple "float" values are
      specified by a COMMA-separated list of values.

      No additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) is defined for this value type.

   Example:

       1000000.0000001
       1.333
       -3.14



Desruisseaux                Standards Track                    [Page 36]

RFC 5545                       iCalendar                  September 2009


3.3.8.  Integer

   Value Name:  INTEGER

   Purpose:  This value type is used to identify properties that contain
      a signed integer value.

   Format Definition:  This value type is defined by the following
      notation:

       integer    = (["+"] / "-") 1*DIGIT

   Description:  If the property permits, multiple "integer" values are
      specified by a COMMA-separated list of values.  The valid range
      for "integer" is -2147483648 to 2147483647.  If the sign is not
      specified, then the value is assumed to be positive.

      No additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) is defined for this value type.

   Example:

       1234567890
       -1234567890
       +1234567890
       432109876

3.3.9.  Period of Time

   Value Name:  PERIOD

   Purpose:  This value type is used to identify values that contain a
      precise period of time.

   Format Definition:  This value type is defined by the following
      notation:

       period     = period-explicit / period-start

       period-explicit = date-time "/" date-time
       ; [ISO.8601.2004] complete representation basic format for a
       ; period of time consisting of a start and end.  The start MUST
       ; be before the end.

       period-start = date-time "/" dur-value
       ; [ISO.8601.2004] complete representation basic format for a
       ; period of time consisting of a start and positive duration
       ; of time.



Desruisseaux                Standards Track                    [Page 37]

RFC 5545                       iCalendar                  September 2009


   Description:  If the property permits, multiple "period" values are
      specified by a COMMA-separated list of values.  There are two
      forms of a period of time.  First, a period of time is identified
      by its start and its end.  This format is based on the
      [ISO.8601.2004] complete representation, basic format for "DATE-
      TIME" start of the period, followed by a SOLIDUS character
      followed by the "DATE-TIME" of the end of the period.  The start
      of the period MUST be before the end of the period.  Second, a
      period of time can also be defined by a start and a positive
      duration of time.  The format is based on the [ISO.8601.2004]
      complete representation, basic format for the "DATE-TIME" start of
      the period, followed by a SOLIDUS character, followed by the
      [ISO.8601.2004] basic format for "DURATION" of the period.

   Example:  The period starting at 18:00:00 UTC, on January 1, 1997 and
      ending at 07:00:00 UTC on January 2, 1997 would be:

       19970101T180000Z/19970102T070000Z

      The period start at 18:00:00 on January 1, 1997 and lasting 5
      hours and 30 minutes would be:

       19970101T180000Z/PT5H30M

      No additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) is defined for this value type.

3.3.10.  Recurrence Rule

   Value Name:  RECUR

   Purpose:  This value type is used to identify properties that contain
      a recurrence rule specification.

   Format Definition:  This value type is defined by the following
      notation:

       recur           = recur-rule-part *( ";" recur-rule-part )
                       ;
                       ; The rule parts are not ordered in any
                       ; particular sequence.
                       ;
                       ; The FREQ rule part is REQUIRED,
                       ; but MUST NOT occur more than once.
                       ;
                       ; The UNTIL or COUNT rule parts are OPTIONAL,
                       ; but they MUST NOT occur in the same 'recur'.
                       ;



Desruisseaux                Standards Track                    [Page 38]

RFC 5545                       iCalendar                  September 2009


                       ; The other rule parts are OPTIONAL,
                       ; but MUST NOT occur more than once.

       recur-rule-part = ( "FREQ" "=" freq )
                       / ( "UNTIL" "=" enddate )
                       / ( "COUNT" "=" 1*DIGIT )
                       / ( "INTERVAL" "=" 1*DIGIT )
                       / ( "BYSECOND" "=" byseclist )
                       / ( "BYMINUTE" "=" byminlist )
                       / ( "BYHOUR" "=" byhrlist )
                       / ( "BYDAY" "=" bywdaylist )
                       / ( "BYMONTHDAY" "=" bymodaylist )
                       / ( "BYYEARDAY" "=" byyrdaylist )
                       / ( "BYWEEKNO" "=" bywknolist )
                       / ( "BYMONTH" "=" bymolist )
                       / ( "BYSETPOS" "=" bysplist )
                       / ( "WKST" "=" weekday )

       freq        = "SECONDLY" / "MINUTELY" / "HOURLY" / "DAILY"
                   / "WEEKLY" / "MONTHLY" / "YEARLY"

       enddate     = date / date-time

       byseclist   = ( seconds *("," seconds) )

       seconds     = 1*2DIGIT       ;0 to 60

       byminlist   = ( minutes *("," minutes) )

       minutes     = 1*2DIGIT       ;0 to 59

       byhrlist    = ( hour *("," hour) )

       hour        = 1*2DIGIT       ;0 to 23

       bywdaylist  = ( weekdaynum *("," weekdaynum) )

       weekdaynum  = [[plus / minus] ordwk] weekday

       plus        = "+"

       minus       = "-"

       ordwk       = 1*2DIGIT       ;1 to 53

       weekday     = "SU" / "MO" / "TU" / "WE" / "TH" / "FR" / "SA"
       ;Corresponding to SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,
       ;FRIDAY, and SATURDAY days of the week.



Desruisseaux                Standards Track                    [Page 39]

RFC 5545                       iCalendar                  September 2009


       bymodaylist = ( monthdaynum *("," monthdaynum) )

       monthdaynum = [plus / minus] ordmoday

       ordmoday    = 1*2DIGIT       ;1 to 31

       byyrdaylist = ( yeardaynum *("," yeardaynum) )

       yeardaynum  = [plus / minus] ordyrday

       ordyrday    = 1*3DIGIT      ;1 to 366

       bywknolist  = ( weeknum *("," weeknum) )

       weeknum     = [plus / minus] ordwk

       bymolist    = ( monthnum *("," monthnum) )

       monthnum    = 1*2DIGIT       ;1 to 12

       bysplist    = ( setposday *("," setposday) )

       setposday   = yeardaynum

   Description:  This value type is a structured value consisting of a
      list of one or more recurrence grammar parts.  Each rule part is
      defined by a NAME=VALUE pair.  The rule parts are separated from
      each other by the SEMICOLON character.  The rule parts are not
      ordered in any particular sequence.  Individual rule parts MUST
      only be specified once.  Compliant applications MUST accept rule
      parts ordered in any sequence, but to ensure backward
      compatibility with applications that pre-date this revision of
      iCalendar the FREQ rule part MUST be the first rule part specified
      in a RECUR value.

      The FREQ rule part identifies the type of recurrence rule.  This
      rule part MUST be specified in the recurrence rule.  Valid values
      include SECONDLY, to specify repeating events based on an interval
      of a second or more; MINUTELY, to specify repeating events based
      on an interval of a minute or more; HOURLY, to specify repeating
      events based on an interval of an hour or more; DAILY, to specify
      repeating events based on an interval of a day or more; WEEKLY, to
      specify repeating events based on an interval of a week or more;
      MONTHLY, to specify repeating events based on an interval of a
      month or more; and YEARLY, to specify repeating events based on an
      interval of a year or more.





Desruisseaux                Standards Track                    [Page 40]

RFC 5545                       iCalendar                  September 2009


      The INTERVAL rule part contains a positive integer representing at
      which intervals the recurrence rule repeats.  The default value is
      "1", meaning every second for a SECONDLY rule, every minute for a
      MINUTELY rule, every hour for an HOURLY rule, every day for a
      DAILY rule, every week for a WEEKLY rule, every month for a
      MONTHLY rule, and every year for a YEARLY rule.  For example,
      within a DAILY rule, a value of "8" means every eight days.

      The UNTIL rule part defines a DATE or DATE-TIME value that bounds
      the recurrence rule in an inclusive manner.  If the value
      specified by UNTIL is synchronized with the specified recurrence,
      this DATE or DATE-TIME becomes the last instance of the
      recurrence.  The value of the UNTIL rule part MUST have the same
      value type as the "DTSTART" property.  Furthermore, if the
      "DTSTART" property is specified as a date with local time, then
      the UNTIL rule part MUST also be specified as a date with local
      time.  If the "DTSTART" property is specified as a date with UTC
      time or a date with local time and time zone reference, then the
      UNTIL rule part MUST be specified as a date with UTC time.  In the
      case of the "STANDARD" and "DAYLIGHT" sub-components the UNTIL
      rule part MUST always be specified as a date with UTC time.  If
      specified as a DATE-TIME value, then it MUST be specified in a UTC
      time format.  If not present, and the COUNT rule part is also not
      present, the "RRULE" is considered to repeat forever.

      The COUNT rule part defines the number of occurrences at which to
      range-bound the recurrence.  The "DTSTART" property value always
      counts as the first occurrence.

      The BYSECOND rule part specifies a COMMA-separated list of seconds
      within a minute.  Valid values are 0 to 60.  The BYMINUTE rule
      part specifies a COMMA-separated list of minutes within an hour.
      Valid values are 0 to 59.  The BYHOUR rule part specifies a COMMA-
      separated list of hours of the day.  Valid values are 0 to 23.
      The BYSECOND, BYMINUTE and BYHOUR rule parts MUST NOT be specified
      when the associated "DTSTART" property has a DATE value type.
      These rule parts MUST be ignored in RECUR value that violate the
      above requirement (e.g., generated by applications that pre-date
      this revision of iCalendar).

      The BYDAY rule part specifies a COMMA-separated list of days of
      the week; SU indicates Sunday; MO indicates Monday; TU indicates
      Tuesday; WE indicates Wednesday; TH indicates Thursday; FR
      indicates Friday; and SA indicates Saturday.

      Each BYDAY value can also be preceded by a positive (+n) or
      negative (-n) integer.  If present, this indicates the nth
      occurrence of a specific day within the MONTHLY or YEARLY "RRULE".



Desruisseaux                Standards Track                    [Page 41]

RFC 5545                       iCalendar                  September 2009


      For example, within a MONTHLY rule, +1MO (or simply 1MO)
      represents the first Monday within the month, whereas -1MO
      represents the last Monday of the month.  The numeric value in a
      BYDAY rule part with the FREQ rule part set to YEARLY corresponds
      to an offset within the month when the BYMONTH rule part is
      present, and corresponds to an offset within the year when the
      BYWEEKNO or BYMONTH rule parts are present.  If an integer
      modifier is not present, it means all days of this type within the
      specified frequency.  For example, within a MONTHLY rule, MO
      represents all Mondays within the month.  The BYDAY rule part MUST
      NOT be specified with a numeric value when the FREQ rule part is
      not set to MONTHLY or YEARLY.  Furthermore, the BYDAY rule part
      MUST NOT be specified with a numeric value with the FREQ rule part
      set to YEARLY when the BYWEEKNO rule part is specified.

      The BYMONTHDAY rule part specifies a COMMA-separated list of days
      of the month.  Valid values are 1 to 31 or -31 to -1.  For
      example, -10 represents the tenth to the last day of the month.
      The BYMONTHDAY rule part MUST NOT be specified when the FREQ rule
      part is set to WEEKLY.

      The BYYEARDAY rule part specifies a COMMA-separated list of days
      of the year.  Valid values are 1 to 366 or -366 to -1.  For
      example, -1 represents the last day of the year (December 31st)
      and -306 represents the 306th to the last day of the year (March
      1st).  The BYYEARDAY rule part MUST NOT be specified when the FREQ
      rule part is set to DAILY, WEEKLY, or MONTHLY.

      The BYWEEKNO rule part specifies a COMMA-separated list of
      ordinals specifying weeks of the year.  Valid values are 1 to 53
      or -53 to -1.  This corresponds to weeks according to week
      numbering as defined in [ISO.8601.2004].  A week is defined as a
      seven day period, starting on the day of the week defined to be
      the week start (see WKST).  Week number one of the calendar year
      is the first week that contains at least four (4) days in that
      calendar year.  This rule part MUST NOT be used when the FREQ rule
      part is set to anything other than YEARLY.  For example, 3
      represents the third week of the year.

         Note: Assuming a Monday week start, week 53 can only occur when
         Thursday is January 1 or if it is a leap year and Wednesday is
         January 1.

      The BYMONTH rule part specifies a COMMA-separated list of months
      of the year.  Valid values are 1 to 12.

      The WKST rule part specifies the day on which the workweek starts.
      Valid values are MO, TU, WE, TH, FR, SA, and SU.  This is



Desruisseaux                Standards Track                    [Page 42]

RFC 5545                       iCalendar                  September 2009


      significant when a WEEKLY "RRULE" has an interval greater than 1,
      and a BYDAY rule part is specified.  This is also significant when
      in a YEARLY "RRULE" when a BYWEEKNO rule part is specified.  The
      default value is MO.

      The BYSETPOS rule part specifies a COMMA-separated list of values
      that corresponds to the nth occurrence within the set of
      recurrence instances specified by the rule.  BYSETPOS operates on
      a set of recurrence instances in one interval of the recurrence
      rule.  For example, in a WEEKLY rule, the interval would be one
      week A set of recurrence instances starts at the beginning of the
      interval defined by the FREQ rule part.  Valid values are 1 to 366
      or -366 to -1.  It MUST only be used in conjunction with another
      BYxxx rule part.  For example "the last work day of the month"
      could be represented as:

       FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1

      Each BYSETPOS value can include a positive (+n) or negative (-n)
      integer.  If present, this indicates the nth occurrence of the
      specific occurrence within the set of occurrences specified by the
      rule.

      Recurrence rules may generate recurrence instances with an invalid
      date (e.g., February 30) or nonexistent local time (e.g., 1:30 AM
      on a day where the local time is moved forward by an hour at 1:00
      AM).  Such recurrence instances MUST be ignored and MUST NOT be
      counted as part of the recurrence set.

      Information, not contained in the rule, necessary to determine the
      various recurrence instance start time and dates are derived from
      the Start Time ("DTSTART") component attribute.  For example,
      "FREQ=YEARLY;BYMONTH=1" doesn't specify a specific day within the
      month or a time.  This information would be the same as what is
      specified for "DTSTART".

      BYxxx rule parts modify the recurrence in some manner.  BYxxx rule
      parts for a period of time that is the same or greater than the
      frequency generally reduce or limit the number of occurrences of
      the recurrence generated.  For example, "FREQ=DAILY;BYMONTH=1"
      reduces the number of recurrence instances from all days (if
      BYMONTH rule part is not present) to all days in January.  BYxxx
      rule parts for a period of time less than the frequency generally
      increase or expand the number of occurrences of the recurrence.
      For example, "FREQ=YEARLY;BYMONTH=1,2" increases the number of
      days within the yearly recurrence set from 1 (if BYMONTH rule part
      is not present) to 2.




Desruisseaux                Standards Track                    [Page 43]

RFC 5545                       iCalendar                  September 2009


      If multiple BYxxx rule parts are specified, then after evaluating
      the specified FREQ and INTERVAL rule parts, the BYxxx rule parts
      are applied to the current set of evaluated occurrences in the
      following order: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY, BYDAY,
      BYHOUR, BYMINUTE, BYSECOND and BYSETPOS; then COUNT and UNTIL are
      evaluated.

      The table below summarizes the dependency of BYxxx rule part
      expand or limit behavior on the FREQ rule part value.

      The term "N/A" means that the corresponding BYxxx rule part MUST
      NOT be used with the corresponding FREQ value.

      BYDAY has some special behavior depending on the FREQ value and
      this is described in separate notes below the table.

   +----------+--------+--------+-------+-------+------+-------+------+
   |          |SECONDLY|MINUTELY|HOURLY |DAILY  |WEEKLY|MONTHLY|YEARLY|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYMONTH   |Limit   |Limit   |Limit  |Limit  |Limit |Limit  |Expand|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYWEEKNO  |N/A     |N/A     |N/A    |N/A    |N/A   |N/A    |Expand|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYYEARDAY |Limit   |Limit   |Limit  |N/A    |N/A   |N/A    |Expand|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYMONTHDAY|Limit   |Limit   |Limit  |Limit  |N/A   |Expand |Expand|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYDAY     |Limit   |Limit   |Limit  |Limit  |Expand|Note 1 |Note 2|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYHOUR    |Limit   |Limit   |Limit  |Expand |Expand|Expand |Expand|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYMINUTE  |Limit   |Limit   |Expand |Expand |Expand|Expand |Expand|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYSECOND  |Limit   |Expand  |Expand |Expand |Expand|Expand |Expand|
   +----------+--------+--------+-------+-------+------+-------+------+
   |BYSETPOS  |Limit   |Limit   |Limit  |Limit  |Limit |Limit  |Limit |
   +----------+--------+--------+-------+-------+------+-------+------+

      Note 1:  Limit if BYMONTHDAY is present; otherwise, special expand
               for MONTHLY.

      Note 2:  Limit if BYYEARDAY or BYMONTHDAY is present; otherwise,
               special expand for WEEKLY if BYWEEKNO present; otherwise,
               special expand for MONTHLY if BYMONTH present; otherwise,
               special expand for YEARLY.






Desruisseaux                Standards Track                    [Page 44]

RFC 5545                       iCalendar                  September 2009


      Here is an example of evaluating multiple BYxxx rule parts.

       DTSTART;TZID=America/New_York:19970105T083000
       RRULE:FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;
        BYMINUTE=30

      First, the "INTERVAL=2" would be applied to "FREQ=YEARLY" to
      arrive at "every other year".  Then, "BYMONTH=1" would be applied
      to arrive at "every January, every other year".  Then, "BYDAY=SU"
      would be applied to arrive at "every Sunday in January, every
      other year".  Then, "BYHOUR=8,9" would be applied to arrive at
      "every Sunday in January at 8 AM and 9 AM, every other year".
      Then, "BYMINUTE=30" would be applied to arrive at "every Sunday in
      January at 8:30 AM and 9:30 AM, every other year".  Then, lacking
      information from "RRULE", the second is derived from "DTSTART", to
      end up in "every Sunday in January at 8:30:00 AM and 9:30:00 AM,
      every other year".  Similarly, if the BYMINUTE, BYHOUR, BYDAY,
      BYMONTHDAY, or BYMONTH rule part were missing, the appropriate
      minute, hour, day, or month would have been retrieved from the
      "DTSTART" property.

      If the computed local start time of a recurrence instance does not
      exist, or occurs more than once, for the specified time zone, the
      time of the recurrence instance is interpreted in the same manner
      as an explicit DATE-TIME value describing that date and time, as
      specified in Section 3.3.5.

      No additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) is defined for this value type.

   Example:  The following is a rule that specifies 10 occurrences that
      occur every other day:

       FREQ=DAILY;COUNT=10;INTERVAL=2

      There are other examples specified in Section 3.8.5.3.

3.3.11.  Text

   Value Name:  TEXT

   Purpose:  This value type is used to identify values that contain
      human-readable text.

   Format Definition:  This value type is defined by the following
      notation:





Desruisseaux                Standards Track                    [Page 45]

RFC 5545                       iCalendar                  September 2009


       text       = *(TSAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
          ; Folded according to description above

       ESCAPED-CHAR = ("\\" / "\;" / "\," / "\N" / "\n")
          ; \\ encodes \, \N or \n encodes newline
          ; \; encodes ;, \, encodes ,

       TSAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-5B /
                    %x5D-7E / NON-US-ASCII
          ; Any character except CONTROLs not needed by the current
          ; character set, DQUOTE, ";", ":", "\", ","

   Description:  If the property permits, multiple TEXT values are
      specified by a COMMA-separated list of values.

      The language in which the text is represented can be controlled by
      the "LANGUAGE" property parameter.

      An intentional formatted text line break MUST only be included in
      a "TEXT" property value by representing the line break with the
      character sequence of BACKSLASH, followed by a LATIN SMALL LETTER
      N or a LATIN CAPITAL LETTER N, that is "\n" or "\N".

      The "TEXT" property values may also contain special characters
      that are used to signify delimiters, such as a COMMA character for
      lists of values or a SEMICOLON character for structured values.
      In order to support the inclusion of these special characters in
      "TEXT" property values, they MUST be escaped with a BACKSLASH
      character.  A BACKSLASH character in a "TEXT" property value MUST
      be escaped with another BACKSLASH character.  A COMMA character in
      a "TEXT" property value MUST be escaped with a BACKSLASH
      character.  A SEMICOLON character in a "TEXT" property value MUST
      be escaped with a BACKSLASH character.  However, a COLON character
      in a "TEXT" property value SHALL NOT be escaped with a BACKSLASH
      character.

   Example:  A multiple line value of:

       Project XYZ Final Review
       Conference Room - 3B
       Come Prepared.

      would be represented as:

       Project XYZ Final Review\nConference Room - 3B\nCome Prepared.






Desruisseaux                Standards Track                    [Page 46]

RFC 5545                       iCalendar                  September 2009


3.3.12.  Time

   Value Name:  TIME

   Purpose:  This value type is used to identify values that contain a
      time of day.

   Format Definition:  This value type is defined by the following
      notation:

       time         = time-hour time-minute time-second [time-utc]

       time-hour    = 2DIGIT        ;00-23
       time-minute  = 2DIGIT        ;00-59
       time-second  = 2DIGIT        ;00-60
       ;The "60" value is used to account for positive "leap" seconds.

       time-utc     = "Z"

   Description:  If the property permits, multiple "time" values are
      specified by a COMMA-separated list of values.  No additional
      content value encoding (i.e., BACKSLASH character encoding, see
      Section 3.3.11) is defined for this value type.

      The "TIME" value type is used to identify values that contain a
      time of day.  The format is based on the [ISO.8601.2004] complete
      representation, basic format for a time of day.  The text format
      consists of a two-digit, 24-hour of the day (i.e., values 00-23),
      two-digit minute in the hour (i.e., values 00-59), and two-digit
      seconds in the minute (i.e., values 00-60).  The seconds value of
      60 MUST only be used to account for positive "leap" seconds.
      Fractions of a second are not supported by this format.

      In parallel to the "DATE-TIME" definition above, the "TIME" value
      type expresses time values in three forms:

      The form of time with UTC offset MUST NOT be used.  For example,
      the following is not valid for a time value:

       230000-0800        ;Invalid time format

      FORM #1 LOCAL TIME

      The local time form is simply a time value that does not contain
      the UTC designator nor does it reference a time zone.  For
      example, 11:00 PM:

       230000



Desruisseaux                Standards Track                    [Page 47]

RFC 5545                       iCalendar                  September 2009


      Time values of this type are said to be "floating" and are not
      bound to any time zone in particular.  They are used to represent
      the same hour, minute, and second value regardless of which time
      zone is currently being observed.  For example, an event can be
      defined that indicates that an individual will be busy from 11:00
      AM to 1:00 PM every day, no matter which time zone the person is
      in.  In these cases, a local time can be specified.  The recipient
      of an iCalendar object with a property value consisting of a local
      time, without any relative time zone information, SHOULD interpret
      the value as being fixed to whatever time zone the "ATTENDEE" is
      in at any given moment.  This means that two "Attendees", may
      participate in the same event at different UTC times; floating
      time SHOULD only be used where that is reasonable behavior.

      In most cases, a fixed time is desired.  To properly communicate a
      fixed time in a property value, either UTC time or local time with
      time zone reference MUST be specified.

      The use of local time in a TIME value without the "TZID" property
      parameter is to be interpreted as floating time, regardless of the
      existence of "VTIMEZONE" calendar components in the iCalendar
      object.

      FORM #2: UTC TIME

      UTC time, or absolute time, is identified by a LATIN CAPITAL
      LETTER Z suffix character, the UTC designator, appended to the
      time value.  For example, the following represents 07:00 AM UTC:

       070000Z

      The "TZID" property parameter MUST NOT be applied to TIME
      properties whose time values are specified in UTC.

      FORM #3: LOCAL TIME AND TIME ZONE REFERENCE

      The local time with reference to time zone information form is
      identified by the use the "TZID" property parameter to reference
      the appropriate time zone definition.  "TZID" is discussed in
      detail in Section 3.2.19.

   Example:  The following represents 8:30 AM in New York in winter,
      five hours behind UTC, in each of the three formats:

       083000
       133000Z
       TZID=America/New_York:083000




Desruisseaux                Standards Track                    [Page 48]

RFC 5545                       iCalendar                  September 2009


3.3.13.  URI

   Value Name:  URI

   Purpose:  This value type is used to identify values that contain a
      uniform resource identifier (URI) type of reference to the
      property value.

   Format Definition:  This value type is defined by the following
      notation:

       uri = <As defined in Section 3 of [RFC3986]>

   Description:  This value type might be used to reference binary
      information, for values that are large, or otherwise undesirable
      to include directly in the iCalendar object.

      Property values with this value type MUST follow the generic URI
      syntax defined in [RFC3986].

      When a property parameter value is a URI value type, the URI MUST
      be specified as a quoted-string value.

      No additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) is defined for this value type.

   Example:  The following is a URI for a network file:

       http://example.com/my-report.txt

3.3.14.  UTC Offset

   Value Name:  UTC-OFFSET

   Purpose:  This value type is used to identify properties that contain
      an offset from UTC to local time.

   Format Definition:  This value type is defined by the following
      notation:

       utc-offset = time-numzone

       time-numzone = ("+" / "-") time-hour time-minute [time-second]

   Description:  The PLUS SIGN character MUST be specified for positive
      UTC offsets (i.e., ahead of UTC).  The HYPHEN-MINUS character MUST
      be specified for negative UTC offsets (i.e., behind of UTC).  The




Desruisseaux                Standards Track                    [Page 49]

RFC 5545                       iCalendar                  September 2009


      value of "-0000" and "-000000" are not allowed.  The time-second,
      if present, MUST NOT be 60; if absent, it defaults to zero.

      No additional content value encoding (i.e., BACKSLASH character
      encoding, see Section 3.3.11) is defined for this value type.

   Example:  The following UTC offsets are given for standard time for
      New York (five hours behind UTC) and Geneva (one hour ahead of
      UTC):

       -0500

       +0100

3.4.  iCalendar Object

   The Calendaring and Scheduling Core Object is a collection of
   calendaring and scheduling information.  Typically, this information
   will consist of an iCalendar stream with a single iCalendar object.
   However, multiple iCalendar objects can be sequentially grouped
   together in an iCalendar stream.  The first line and last line of the
   iCalendar object MUST contain a pair of iCalendar object delimiter
   strings.  The syntax for an iCalendar stream is as follows:

       icalstream = 1*icalobject

       icalobject = "BEGIN" ":" "VCALENDAR" CRLF
                    icalbody
                    "END" ":" "VCALENDAR" CRLF

   The following is a simple example of an iCalendar object:

       BEGIN:VCALENDAR
       VERSION:2.0
       PRODID:-//hacksw/handcal//NONSGML v1.0//EN
       BEGIN:VEVENT
       UID:19970610T172345Z-AF23B2@example.com
       DTSTAMP:19970610T172345Z
       DTSTART:19970714T170000Z
       DTEND:19970715T040000Z
       SUMMARY:Bastille Day Party
       END:VEVENT
       END:VCALENDAR








Desruisseaux                Standards Track                    [Page 50]

RFC 5545                       iCalendar                  September 2009


3.5.  Property

   A property is the definition of an individual attribute describing a
   calendar object or a calendar component.  A property takes the form
   defined by the "contentline" notation defined in Section 3.1.

   The following is an example of a property:

       DTSTART:19960415T133000Z

   This memo imposes no ordering of properties within an iCalendar
   object.

   Property names, parameter names, and enumerated parameter values are
   case-insensitive.  For example, the property name "DUE" is the same
   as "due" and "Due", DTSTART;TZID=America/New_York:19980714T120000 is
   the same as DtStart;TzID=America/New_York:19980714T120000.

3.6.  Calendar Components

   The body of the iCalendar object consists of a sequence of calendar
   properties and one or more calendar components.  The calendar
   properties are attributes that apply to the calendar object as a
   whole.  The calendar components are collections of properties that
   express a particular calendar semantic.  For example, the calendar
   component can specify an event, a to-do, a journal entry, time zone
   information, free/busy time information, or an alarm.

   The body of the iCalendar object is defined by the following
   notation:

       icalbody   = calprops component

       calprops   = *(
                  ;
                  ; The following are REQUIRED,
                  ; but MUST NOT occur more than once.
                  ;
                  prodid / version /
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  calscale / method /
                  ;
                  ; The following are OPTIONAL,
                  ; and MAY occur more than once.
                  ;



Desruisseaux                Standards Track                    [Page 51]

RFC 5545                       iCalendar                  September 2009


                  x-prop / iana-prop
                  ;
                  )

       component  = 1*(eventc / todoc / journalc / freebusyc /
                    timezonec / iana-comp / x-comp)

       iana-comp  = "BEGIN" ":" iana-token CRLF
                    1*contentline
                    "END" ":" iana-token CRLF

       x-comp     = "BEGIN" ":" x-name CRLF
                    1*contentline
                    "END" ":" x-name CRLF

   An iCalendar object MUST include the "PRODID" and "VERSION" calendar
   properties.  In addition, it MUST include at least one calendar
   component.  Special forms of iCalendar objects are possible to
   publish just busy time (i.e., only a "VFREEBUSY" calendar component)
   or time zone (i.e., only a "VTIMEZONE" calendar component)
   information.  In addition, a complex iCalendar object that is used to
   capture a complete snapshot of the contents of a calendar is possible
   (e.g., composite of many different calendar components).  More
   commonly, an iCalendar object will consist of just a single "VEVENT",
   "VTODO", or "VJOURNAL" calendar component.  Applications MUST ignore
   x-comp and iana-comp values they don't recognize.  Applications that
   support importing iCalendar objects SHOULD support all of the
   component types defined in this document, and SHOULD NOT silently
   drop any components as that can lead to user data loss.

3.6.1.  Event Component

   Component Name:  VEVENT

   Purpose:  Provide a grouping of component properties that describe an
      event.

   Format Definition:  A "VEVENT" calendar component is defined by the
      following notation:

       eventc     = "BEGIN" ":" "VEVENT" CRLF
                    eventprop *alarmc
                    "END" ":" "VEVENT" CRLF

       eventprop  = *(
                  ;
                  ; The following are REQUIRED,
                  ; but MUST NOT occur more than once.



Desruisseaux                Standards Track                    [Page 52]

RFC 5545                       iCalendar                  September 2009


                  ;
                  dtstamp / uid /
                  ;
                  ; The following is REQUIRED if the component
                  ; appears in an iCalendar object that doesn't
                  ; specify the "METHOD" property; otherwise, it
                  ; is OPTIONAL; in any case, it MUST NOT occur
                  ; more than once.
                  ;
                  dtstart /
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  class / created / description / geo /
                  last-mod / location / organizer / priority /
                  seq / status / summary / transp /
                  url / recurid /
                  ;
                  ; The following is OPTIONAL,
                  ; but SHOULD NOT occur more than once.
                  ;
                  rrule /
                  ;
                  ; Either 'dtend' or 'duration' MAY appear in
                  ; a 'eventprop', but 'dtend' and 'duration'
                  ; MUST NOT occur in the same 'eventprop'.
                  ;
                  dtend / duration /
                  ;
                  ; The following are OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  attach / attendee / categories / comment /
                  contact / exdate / rstatus / related /
                  resources / rdate / x-prop / iana-prop
                  ;
                  )

   Description:  A "VEVENT" calendar component is a grouping of
      component properties, possibly including "VALARM" calendar
      components, that represents a scheduled amount of time on a
      calendar.  For example, it can be an activity; such as a one-hour
      long, department meeting from 8:00 AM to 9:00 AM, tomorrow.
      Generally, an event will take up time on an individual calendar.
      Hence, the event will appear as an opaque interval in a search for
      busy time.  Alternately, the event can have its Time Transparency




Desruisseaux                Standards Track                    [Page 53]

RFC 5545                       iCalendar                  September 2009


      set to "TRANSPARENT" in order to prevent blocking of the event in
      searches for busy time.

      The "VEVENT" is also the calendar component used to specify an
      anniversary or daily reminder within a calendar.  These events
      have a DATE value type for the "DTSTART" property instead of the
      default value type of DATE-TIME.  If such a "VEVENT" has a "DTEND"
      property, it MUST be specified as a DATE value also.  The
      anniversary type of "VEVENT" can span more than one date (i.e.,
      "DTEND" property value is set to a calendar date after the
      "DTSTART" property value).  If such a "VEVENT" has a "DURATION"
      property, it MUST be specified as a "dur-day" or "dur-week" value.

      The "DTSTART" property for a "VEVENT" specifies the inclusive
      start of the event.  For recurring events, it also specifies the
      very first instance in the recurrence set.  The "DTEND" property
      for a "VEVENT" calendar component specifies the non-inclusive end
      of the event.  For cases where a "VEVENT" calendar component
      specifies a "DTSTART" property with a DATE value type but no
      "DTEND" nor "DURATION" property, the event's duration is taken to
      be one day.  For cases where a "VEVENT" calendar component
      specifies a "DTSTART" property with a DATE-TIME value type but no
      "DTEND" property, the event ends on the same calendar date and
      time of day specified by the "DTSTART" property.

      The "VEVENT" calendar component cannot be nested within another
      calendar component.  However, "VEVENT" calendar components can be
      related to each other or to a "VTODO" or to a "VJOURNAL" calendar
      component with the "RELATED-TO" property.

   Example:  The following is an example of the "VEVENT" calendar
      component used to represent a meeting that will also be opaque to
      searches for busy time:

       BEGIN:VEVENT
       UID:19970901T130000Z-123401@example.com
       DTSTAMP:19970901T130000Z
       DTSTART:19970903T163000Z
       DTEND:19970903T190000Z
       SUMMARY:Annual Employee Review
       CLASS:PRIVATE
       CATEGORIES:BUSINESS,HUMAN RESOURCES
       END:VEVENT

      The following is an example of the "VEVENT" calendar component
      used to represent a reminder that will not be opaque, but rather
      transparent, to searches for busy time:




Desruisseaux                Standards Track                    [Page 54]

RFC 5545                       iCalendar                  September 2009


       BEGIN:VEVENT
       UID:19970901T130000Z-123402@example.com
       DTSTAMP:19970901T130000Z
       DTSTART:19970401T163000Z
       DTEND:19970402T010000Z
       SUMMARY:Laurel is in sensitivity awareness class.
       CLASS:PUBLIC
       CATEGORIES:BUSINESS,HUMAN RESOURCES
       TRANSP:TRANSPARENT
       END:VEVENT

      The following is an example of the "VEVENT" calendar component
      used to represent an anniversary that will occur annually:

       BEGIN:VEVENT
       UID:19970901T130000Z-123403@example.com
       DTSTAMP:19970901T130000Z
       DTSTART;VALUE=DATE:19971102
       SUMMARY:Our Blissful Anniversary
       TRANSP:TRANSPARENT
       CLASS:CONFIDENTIAL
       CATEGORIES:ANNIVERSARY,PERSONAL,SPECIAL OCCASION
       RRULE:FREQ=YEARLY
       END:VEVENT

      The following is an example of the "VEVENT" calendar component
      used to represent a multi-day event scheduled from June 28th, 2007
      to July 8th, 2007 inclusively.  Note that the "DTEND" property is
      set to July 9th, 2007, since the "DTEND" property specifies the
      non-inclusive end of the event.

       BEGIN:VEVENT
       UID:20070423T123432Z-541111@example.com
       DTSTAMP:20070423T123432Z
       DTSTART;VALUE=DATE:20070628
       DTEND;VALUE=DATE:20070709
       SUMMARY:Festival International de Jazz de Montreal
       TRANSP:TRANSPARENT
       END:VEVENT

3.6.2.  To-Do Component

   Component Name:  VTODO

   Purpose:  Provide a grouping of calendar properties that describe a
      to-do.





Desruisseaux                Standards Track                    [Page 55]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  A "VTODO" calendar component is defined by the
      following notation:

       todoc      = "BEGIN" ":" "VTODO" CRLF
                    todoprop *alarmc
                    "END" ":" "VTODO" CRLF

       todoprop   = *(
                  ;
                  ; The following are REQUIRED,
                  ; but MUST NOT occur more than once.
                  ;
                  dtstamp / uid /
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  class / completed / created / description /
                  dtstart / geo / last-mod / location / organizer /
                  percent / priority / recurid / seq / status /
                  summary / url /
                  ;
                  ; The following is OPTIONAL,
                  ; but SHOULD NOT occur more than once.
                  ;
                  rrule /
                  ;
                  ; Either 'due' or 'duration' MAY appear in
                  ; a 'todoprop', but 'due' and 'duration'
                  ; MUST NOT occur in the same 'todoprop'.
                  ; If 'duration' appear in a 'todoprop',
                  ; then 'dtstart' MUST also appear in
                  ; the same 'todoprop'.
                  ;
                  due / duration /
                  ;
                  ; The following are OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  attach / attendee / categories / comment / contact /
                  exdate / rstatus / related / resources /
                  rdate / x-prop / iana-prop
                  ;
                  )

   Description:  A "VTODO" calendar component is a grouping of component
      properties and possibly "VALARM" calendar components that
      represent an action-item or assignment.  For example, it can be



Desruisseaux                Standards Track                    [Page 56]

RFC 5545                       iCalendar                  September 2009


      used to represent an item of work assigned to an individual; such
      as "turn in travel expense today".

      The "VTODO" calendar component cannot be nested within another
      calendar component.  However, "VTODO" calendar components can be
      related to each other or to a "VEVENT" or to a "VJOURNAL" calendar
      component with the "RELATED-TO" property.

      A "VTODO" calendar component without the "DTSTART" and "DUE" (or
      "DURATION") properties specifies a to-do that will be associated
      with each successive calendar date, until it is completed.

   Examples:  The following is an example of a "VTODO" calendar
      component that needs to be completed before May 1st, 2007.  On
      midnight May 1st, 2007 this to-do would be considered overdue.

       BEGIN:VTODO
       UID:20070313T123432Z-456553@example.com
       DTSTAMP:20070313T123432Z
       DUE;VALUE=DATE:20070501
       SUMMARY:Submit Quebec Income Tax Return for 2006
       CLASS:CONFIDENTIAL
       CATEGORIES:FAMILY,FINANCE
       STATUS:NEEDS-ACTION
       END:VTODO

      The following is an example of a "VTODO" calendar component that
      was due before 1:00 P.M. UTC on July 9th, 2007 and was completed
      on July 7th, 2007 at 10:00 A.M. UTC.

       BEGIN:VTODO
       UID:20070514T103211Z-123404@example.com
       DTSTAMP:20070514T103211Z
       DTSTART:20070514T110000Z
       DUE:20070709T130000Z
       COMPLETED:20070707T100000Z
       SUMMARY:Submit Revised Internet-Draft
       PRIORITY:1
       STATUS:NEEDS-ACTION
       END:VTODO

3.6.3.  Journal Component

   Component Name:  VJOURNAL

   Purpose:  Provide a grouping of component properties that describe a
      journal entry.




Desruisseaux                Standards Track                    [Page 57]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  A "VJOURNAL" calendar component is defined by the
      following notation:

       journalc   = "BEGIN" ":" "VJOURNAL" CRLF
                    jourprop
                    "END" ":" "VJOURNAL" CRLF

       jourprop   = *(
                  ;
                  ; The following are REQUIRED,
                  ; but MUST NOT occur more than once.
                  ;
                  dtstamp / uid /
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  class / created / dtstart /
                  last-mod / organizer / recurid / seq /
                  status / summary / url /
                  ;
                  ; The following is OPTIONAL,
                  ; but SHOULD NOT occur more than once.
                  ;
                  rrule /
                  ;
                  ; The following are OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  attach / attendee / categories / comment /
                  contact / description / exdate / related / rdate /
                  rstatus / x-prop / iana-prop
                  ;
                  )

   Description:  A "VJOURNAL" calendar component is a grouping of
      component properties that represent one or more descriptive text
      notes associated with a particular calendar date.  The "DTSTART"
      property is used to specify the calendar date with which the
      journal entry is associated.  Generally, it will have a DATE value
      data type, but it can also be used to specify a DATE-TIME value
      data type.  Examples of a journal entry include a daily record of
      a legislative body or a journal entry of individual telephone
      contacts for the day or an ordered list of accomplishments for the
      day.  The "VJOURNAL" calendar component can also be used to
      associate a document with a calendar date.





Desruisseaux                Standards Track                    [Page 58]

RFC 5545                       iCalendar                  September 2009


      The "VJOURNAL" calendar component does not take up time on a
      calendar.  Hence, it does not play a role in free or busy time
      searches -- it is as though it has a time transparency value of
      TRANSPARENT.  It is transparent to any such searches.

      The "VJOURNAL" calendar component cannot be nested within another
      calendar component.  However, "VJOURNAL" calendar components can
      be related to each other or to a "VEVENT" or to a "VTODO" calendar
      component, with the "RELATED-TO" property.

   Example:  The following is an example of the "VJOURNAL" calendar
      component:

       BEGIN:VJOURNAL
       UID:19970901T130000Z-123405@example.com
       DTSTAMP:19970901T130000Z
       DTSTART;VALUE=DATE:19970317
       SUMMARY:Staff meeting minutes
       DESCRIPTION:1. Staff meeting: Participants include Joe\,
         Lisa\, and Bob. Aurora project plans were reviewed.
         There is currently no budget reserves for this project.
         Lisa will escalate to management. Next meeting on Tuesday.\n
        2. Telephone Conference: ABC Corp. sales representative
         called to discuss new printer. Promised to get us a demo by
         Friday.\n3. Henry Miller (Handsoff Insurance): Car was
         totaled by tree. Is looking into a loaner car. 555-2323
         (tel).
       END:VJOURNAL

3.6.4.  Free/Busy Component

   Component Name:  VFREEBUSY

   Purpose:  Provide a grouping of component properties that describe
      either a request for free/busy time, describe a response to a
      request for free/busy time, or describe a published set of busy
      time.

   Format Definition:  A "VFREEBUSY" calendar component is defined by
      the following notation:

       freebusyc  = "BEGIN" ":" "VFREEBUSY" CRLF
                    fbprop
                    "END" ":" "VFREEBUSY" CRLF

       fbprop     = *(
                  ;
                  ; The following are REQUIRED,



Desruisseaux                Standards Track                    [Page 59]

RFC 5545                       iCalendar                  September 2009


                  ; but MUST NOT occur more than once.
                  ;
                  dtstamp / uid /
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  contact / dtstart / dtend /
                  organizer / url /
                  ;
                  ; The following are OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  attendee / comment / freebusy / rstatus / x-prop /
                  iana-prop
                  ;
                  )

   Description:  A "VFREEBUSY" calendar component is a grouping of
      component properties that represents either a request for free or
      busy time information, a reply to a request for free or busy time
      information, or a published set of busy time information.

      When used to request free/busy time information, the "ATTENDEE"
      property specifies the calendar users whose free/busy time is
      being requested; the "ORGANIZER" property specifies the calendar
      user who is requesting the free/busy time; the "DTSTART" and
      "DTEND" properties specify the window of time for which the free/
      busy time is being requested; the "UID" and "DTSTAMP" properties
      are specified to assist in proper sequencing of multiple free/busy
      time requests.

      When used to reply to a request for free/busy time, the "ATTENDEE"
      property specifies the calendar user responding to the free/busy
      time request; the "ORGANIZER" property specifies the calendar user
      that originally requested the free/busy time; the "FREEBUSY"
      property specifies the free/busy time information (if it exists);
      and the "UID" and "DTSTAMP" properties are specified to assist in
      proper sequencing of multiple free/busy time replies.

      When used to publish busy time, the "ORGANIZER" property specifies
      the calendar user associated with the published busy time; the
      "DTSTART" and "DTEND" properties specify an inclusive time window
      that surrounds the busy time information; the "FREEBUSY" property
      specifies the published busy time information; and the "DTSTAMP"
      property specifies the DATE-TIME that iCalendar object was
      created.




Desruisseaux                Standards Track                    [Page 60]

RFC 5545                       iCalendar                  September 2009


      The "VFREEBUSY" calendar component cannot be nested within another
      calendar component.  Multiple "VFREEBUSY" calendar components can
      be specified within an iCalendar object.  This permits the
      grouping of free/busy information into logical collections, such
      as monthly groups of busy time information.

      The "VFREEBUSY" calendar component is intended for use in
      iCalendar object methods involving requests for free time,
      requests for busy time, requests for both free and busy, and the
      associated replies.

      Free/Busy information is represented with the "FREEBUSY" property.
      This property provides a terse representation of time periods.
      One or more "FREEBUSY" properties can be specified in the
      "VFREEBUSY" calendar component.

      When present in a "VFREEBUSY" calendar component, the "DTSTART"
      and "DTEND" properties SHOULD be specified prior to any "FREEBUSY"
      properties.

      The recurrence properties ("RRULE", "RDATE", "EXDATE") are not
      permitted within a "VFREEBUSY" calendar component.  Any recurring
      events are resolved into their individual busy time periods using
      the "FREEBUSY" property.

   Example:  The following is an example of a "VFREEBUSY" calendar
      component used to request free or busy time information:

       BEGIN:VFREEBUSY
       UID:19970901T082949Z-FA43EF@example.com
       ORGANIZER:mailto:jane_doe@example.com
       ATTENDEE:mailto:john_public@example.com
       DTSTART:19971015T050000Z
       DTEND:19971016T050000Z
       DTSTAMP:19970901T083000Z
       END:VFREEBUSY















Desruisseaux                Standards Track                    [Page 61]

RFC 5545                       iCalendar                  September 2009


      The following is an example of a "VFREEBUSY" calendar component
      used to reply to the request with busy time information:

       BEGIN:VFREEBUSY
       UID:19970901T095957Z-76A912@example.com
       ORGANIZER:mailto:jane_doe@example.com
       ATTENDEE:mailto:john_public@example.com
       DTSTAMP:19970901T100000Z
       FREEBUSY:19971015T050000Z/PT8H30M,
        19971015T160000Z/PT5H30M,19971015T223000Z/PT6H30M
       URL:http://example.com/pub/busy/jpublic-01.ifb
       COMMENT:This iCalendar file contains busy time information for
         the next three months.
       END:VFREEBUSY

      The following is an example of a "VFREEBUSY" calendar component
      used to publish busy time information:

       BEGIN:VFREEBUSY
       UID:19970901T115957Z-76A912@example.com
       DTSTAMP:19970901T120000Z
       ORGANIZER:jsmith@example.com
       DTSTART:19980313T141711Z
       DTEND:19980410T141711Z
       FREEBUSY:19980314T233000Z/19980315T003000Z
       FREEBUSY:19980316T153000Z/19980316T163000Z
       FREEBUSY:19980318T030000Z/19980318T040000Z
       URL:http://www.example.com/calendar/busytime/jsmith.ifb
       END:VFREEBUSY

3.6.5.  Time Zone Component

   Component Name:  VTIMEZONE

   Purpose:  Provide a grouping of component properties that defines a
      time zone.

   Format Definition:  A "VTIMEZONE" calendar component is defined by
      the following notation:

       timezonec  = "BEGIN" ":" "VTIMEZONE" CRLF
                    *(
                    ;
                    ; 'tzid' is REQUIRED, but MUST NOT occur more
                    ; than once.
                    ;
                    tzid /
                    ;



Desruisseaux                Standards Track                    [Page 62]

RFC 5545                       iCalendar                  September 2009


                    ; 'last-mod' and 'tzurl' are OPTIONAL,
                    ; but MUST NOT occur more than once.
                    ;
                    last-mod / tzurl /
                    ;
                    ; One of 'standardc' or 'daylightc' MUST occur
                    ; and each MAY occur more than once.
                    ;
                    standardc / daylightc /
                    ;
                    ; The following are OPTIONAL,
                    ; and MAY occur more than once.
                    ;
                    x-prop / iana-prop
                    ;
                    )
                    "END" ":" "VTIMEZONE" CRLF

       standardc  = "BEGIN" ":" "STANDARD" CRLF
                    tzprop
                    "END" ":" "STANDARD" CRLF

       daylightc  = "BEGIN" ":" "DAYLIGHT" CRLF
                    tzprop
                    "END" ":" "DAYLIGHT" CRLF

       tzprop     = *(
                    ;
                    ; The following are REQUIRED,
                    ; but MUST NOT occur more than once.
                    ;
                    dtstart / tzoffsetto / tzoffsetfrom /
                    ;
                    ; The following is OPTIONAL,
                    ; but SHOULD NOT occur more than once.
                    ;
                    rrule /
                    ;
                    ; The following are OPTIONAL,
                    ; and MAY occur more than once.
                    ;
                    comment / rdate / tzname / x-prop / iana-prop
                    ;
                    )

   Description:  A time zone is unambiguously defined by the set of time
      measurement rules determined by the governing body for a given
      geographic area.  These rules describe, at a minimum, the base



Desruisseaux                Standards Track                    [Page 63]

RFC 5545                       iCalendar                  September 2009


      offset from UTC for the time zone, often referred to as the
      Standard Time offset.  Many locations adjust their Standard Time
      forward or backward by one hour, in order to accommodate seasonal
      changes in number of daylight hours, often referred to as Daylight
      Saving Time.  Some locations adjust their time by a fraction of an
      hour.  Standard Time is also known as Winter Time.  Daylight
      Saving Time is also known as Advanced Time, Summer Time, or Legal
      Time in certain countries.  The following table shows the changes
      in time zone rules in effect for New York City starting from 1967.
      Each line represents a description or rule for a particular
      observance.

                         Effective Observance Rule

     +-----------+--------------------------+--------+--------------+
     | Date      | (Date-Time)              | Offset | Abbreviation |
     +-----------+--------------------------+--------+--------------+
     | 1967-1973 | last Sun in Apr, 02:00   | -0400  | EDT          |
     |           |                          |        |              |
     | 1967-2006 | last Sun in Oct, 02:00   | -0500  | EST          |
     |           |                          |        |              |
     | 1974-1974 | Jan 6, 02:00             | -0400  | EDT          |
     |           |                          |        |              |
     | 1975-1975 | Feb 23, 02:00            | -0400  | EDT          |
     |           |                          |        |              |
     | 1976-1986 | last Sun in Apr, 02:00   | -0400  | EDT          |
     |           |                          |        |              |
     | 1987-2006 | first Sun in Apr, 02:00  | -0400  | EDT          |
     |           |                          |        |              |
     | 2007-*    | second Sun in Mar, 02:00 | -0400  | EDT          |
     |           |                          |        |              |
     | 2007-*    | first Sun in Nov, 02:00  | -0500  | EST          |
     +-----------+--------------------------+--------+--------------+

   Note: The specification of a global time zone registry is not
         addressed by this document and is left for future study.
         However, implementers may find the TZ database [TZDB] a useful
         reference.  It is an informal, public-domain collection of time
         zone information, which is currently being maintained by
         volunteer Internet participants, and is used in several
         operating systems.  This database contains current and
         historical time zone information for a wide variety of
         locations around the globe; it provides a time zone identifier
         for every unique time zone rule set in actual use since 1970,
         with historical data going back to the introduction of standard
         time.





Desruisseaux                Standards Track                    [Page 64]

RFC 5545                       iCalendar                  September 2009


      Interoperability between two calendaring and scheduling
      applications, especially for recurring events, to-dos or journal
      entries, is dependent on the ability to capture and convey date
      and time information in an unambiguous format.  The specification
      of current time zone information is integral to this behavior.

      If present, the "VTIMEZONE" calendar component defines the set of
      Standard Time and Daylight Saving Time observances (or rules) for
      a particular time zone for a given interval of time.  The
      "VTIMEZONE" calendar component cannot be nested within other
      calendar components.  Multiple "VTIMEZONE" calendar components can
      exist in an iCalendar object.  In this situation, each "VTIMEZONE"
      MUST represent a unique time zone definition.  This is necessary
      for some classes of events, such as airline flights, that start in
      one time zone and end in another.

      The "VTIMEZONE" calendar component MUST include the "TZID"
      property and at least one definition of a "STANDARD" or "DAYLIGHT"
      sub-component.  The "STANDARD" or "DAYLIGHT" sub-component MUST
      include the "DTSTART", "TZOFFSETFROM", and "TZOFFSETTO"
      properties.

      An individual "VTIMEZONE" calendar component MUST be specified for
      each unique "TZID" parameter value specified in the iCalendar
      object.  In addition, a "VTIMEZONE" calendar component, referred
      to by a recurring calendar component, MUST provide valid time zone
      information for all recurrence instances.

      Each "VTIMEZONE" calendar component consists of a collection of
      one or more sub-components that describe the rule for a particular
      observance (either a Standard Time or a Daylight Saving Time
      observance).  The "STANDARD" sub-component consists of a
      collection of properties that describe Standard Time.  The
      "DAYLIGHT" sub-component consists of a collection of properties
      that describe Daylight Saving Time.  In general, this collection
      of properties consists of:

      *  the first onset DATE-TIME for the observance;

      *  the last onset DATE-TIME for the observance, if a last onset is
         known;

      *  the offset to be applied for the observance;

      *  a rule that describes the day and time when the observance
         takes effect;

      *  an optional name for the observance.



Desruisseaux                Standards Track                    [Page 65]

RFC 5545                       iCalendar                  September 2009


      For a given time zone, there may be multiple unique definitions of
      the observances over a period of time.  Each observance is
      described using either a "STANDARD" or "DAYLIGHT" sub-component.
      The collection of these sub-components is used to describe the
      time zone for a given period of time.  The offset to apply at any
      given time is found by locating the observance that has the last
      onset date and time before the time in question, and using the
      offset value from that observance.

      The top-level properties in a "VTIMEZONE" calendar component are:

      The mandatory "TZID" property is a text value that uniquely
      identifies the "VTIMEZONE" calendar component within the scope of
      an iCalendar object.

      The optional "LAST-MODIFIED" property is a UTC value that
      specifies the date and time that this time zone definition was
      last updated.

      The optional "TZURL" property is a url value that points to a
      published "VTIMEZONE" definition.  "TZURL" SHOULD refer to a
      resource that is accessible by anyone who might need to interpret
      the object.  This SHOULD NOT normally be a "file" URL or other URL
      that is not widely accessible.

      The collection of properties that are used to define the
      "STANDARD" and "DAYLIGHT" sub-components include:

      The mandatory "DTSTART" property gives the effective onset date
      and local time for the time zone sub-component definition.
      "DTSTART" in this usage MUST be specified as a date with a local
      time value.

      The mandatory "TZOFFSETFROM" property gives the UTC offset that is
      in use when the onset of this time zone observance begins.
      "TZOFFSETFROM" is combined with "DTSTART" to define the effective
      onset for the time zone sub-component definition.  For example,
      the following represents the time at which the observance of
      Standard Time took effect in Fall 1967 for New York City:

       DTSTART:19671029T020000

       TZOFFSETFROM:-0400

      The mandatory "TZOFFSETTO" property gives the UTC offset for the
      time zone sub-component (Standard Time or Daylight Saving Time)
      when this observance is in use.




Desruisseaux                Standards Track                    [Page 66]

RFC 5545                       iCalendar                  September 2009


      The optional "TZNAME" property is the customary name for the time
      zone.  This could be used for displaying dates.

      The onset DATE-TIME values for the observance defined by the time
      zone sub-component is defined by the "DTSTART", "RRULE", and
      "RDATE" properties.

      The "RRULE" property defines the recurrence rule for the onset of
      the observance defined by this time zone sub-component.  Some
      specific requirements for the usage of "RRULE" for this purpose
      include:

      *  If observance is known to have an effective end date, the
         "UNTIL" recurrence rule parameter MUST be used to specify the
         last valid onset of this observance (i.e., the UNTIL DATE-TIME
         will be equal to the last instance generated by the recurrence
         pattern).  It MUST be specified in UTC time.

      *  The "DTSTART" and the "TZOFFSETFROM" properties MUST be used
         when generating the onset DATE-TIME values (instances) from the
         "RRULE".

      The "RDATE" property can also be used to define the onset of the
      observance by giving the individual onset date and times.  "RDATE"
      in this usage MUST be specified as a date with local time value,
      relative to the UTC offset specified in the "TZOFFSETFROM"
      property.

      The optional "COMMENT" property is also allowed for descriptive
      explanatory text.

   Example:  The following are examples of the "VTIMEZONE" calendar
      component:

      This is an example showing all the time zone rules for New York
      City since April 30, 1967 at 03:00:00 EDT.

       BEGIN:VTIMEZONE
       TZID:America/New_York
       LAST-MODIFIED:20050809T050000Z
       BEGIN:DAYLIGHT
       DTSTART:19670430T020000
       RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=-1SU;UNTIL=19730429T070000Z
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       BEGIN:STANDARD



Desruisseaux                Standards Track                    [Page 67]

RFC 5545                       iCalendar                  September 2009


       DTSTART:19671029T020000
       RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU;UNTIL=20061029T060000Z
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:19740106T020000
       RDATE:19750223T020000
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       BEGIN:DAYLIGHT
       DTSTART:19760425T020000
       RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=-1SU;UNTIL=19860427T070000Z
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       BEGIN:DAYLIGHT
       DTSTART:19870405T020000
       RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=1SU;UNTIL=20060402T070000Z
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       BEGIN:DAYLIGHT
       DTSTART:20070311T020000
       RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       BEGIN:STANDARD
       DTSTART:20071104T020000
       RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       END:VTIMEZONE

      This is an example showing time zone information for New York City
      using only the "DTSTART" property.  Note that this is only
      suitable for a recurring event that starts on or later than March
      11, 2007 at 03:00:00 EDT (i.e., the earliest effective transition
      date and time) and ends no later than March 9, 2008 at 01:59:59



Desruisseaux                Standards Track                    [Page 68]

RFC 5545                       iCalendar                  September 2009


      EST (i.e., latest valid date and time for EST in this scenario).
      For example, this can be used for a recurring event that occurs
      every Friday, 8:00 A.M.-9:00 A.M., starting June 1, 2007, ending
      December 31, 2007,

       BEGIN:VTIMEZONE
       TZID:America/New_York
       LAST-MODIFIED:20050809T050000Z
       BEGIN:STANDARD
       DTSTART:20071104T020000
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:20070311T020000
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE

      This is a simple example showing the current time zone rules for
      New York City using a "RRULE" recurrence pattern.  Note that there
      is no effective end date to either of the Standard Time or
      Daylight Time rules.  This information would be valid for a
      recurring event starting today and continuing indefinitely.

       BEGIN:VTIMEZONE
       TZID:America/New_York
       LAST-MODIFIED:20050809T050000Z
       TZURL:http://zones.example.com/tz/America-New_York.ics
       BEGIN:STANDARD
       DTSTART:20071104T020000
       RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:20070311T020000
       RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE




Desruisseaux                Standards Track                    [Page 69]

RFC 5545                       iCalendar                  September 2009


      This is an example showing a set of rules for a fictitious time
      zone where the Daylight Time rule has an effective end date (i.e.,
      after that date, Daylight Time is no longer observed).

       BEGIN:VTIMEZONE
       TZID:Fictitious
       LAST-MODIFIED:19870101T000000Z
       BEGIN:STANDARD
       DTSTART:19671029T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:19870405T020000
       RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE





























Desruisseaux                Standards Track                    [Page 70]

RFC 5545                       iCalendar                  September 2009


      This is an example showing a set of rules for a fictitious time
      zone where the first Daylight Time rule has an effective end date.
      There is a second Daylight Time rule that picks up where the other
      left off.

       BEGIN:VTIMEZONE
       TZID:Fictitious
       LAST-MODIFIED:19870101T000000Z
       BEGIN:STANDARD
       DTSTART:19671029T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:19870405T020000
       RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       BEGIN:DAYLIGHT
       DTSTART:19990424T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=4
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE

3.6.6.  Alarm Component

   Component Name:  VALARM

   Purpose:  Provide a grouping of component properties that define an
      alarm.

   Format Definition:  A "VALARM" calendar component is defined by the
      following notation:

       alarmc     = "BEGIN" ":" "VALARM" CRLF
                    (audioprop / dispprop / emailprop)
                    "END" ":" "VALARM" CRLF

       audioprop  = *(
                  ;
                  ; 'action' and 'trigger' are both REQUIRED,



Desruisseaux                Standards Track                    [Page 71]

RFC 5545                       iCalendar                  September 2009


                  ; but MUST NOT occur more than once.
                  ;
                  action / trigger /
                  ;
                  ; 'duration' and 'repeat' are both OPTIONAL,
                  ; and MUST NOT occur more than once each;
                  ; but if one occurs, so MUST the other.
                  ;
                  duration / repeat /
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  attach /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  x-prop / iana-prop
                  ;
                  )

       dispprop   = *(
                  ;
                  ; The following are REQUIRED,
                  ; but MUST NOT occur more than once.
                  ;
                  action / description / trigger /
                  ;
                  ; 'duration' and 'repeat' are both OPTIONAL,
                  ; and MUST NOT occur more than once each;
                  ; but if one occurs, so MUST the other.
                  ;
                  duration / repeat /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  x-prop / iana-prop
                  ;
                  )

       emailprop  = *(
                  ;
                  ; The following are all REQUIRED,
                  ; but MUST NOT occur more than once.
                  ;
                  action / description / trigger / summary /



Desruisseaux                Standards Track                    [Page 72]

RFC 5545                       iCalendar                  September 2009


                  ;
                  ; The following is REQUIRED,
                  ; and MAY occur more than once.
                  ;
                  attendee /
                  ;
                  ; 'duration' and 'repeat' are both OPTIONAL,
                  ; and MUST NOT occur more than once each;
                  ; but if one occurs, so MUST the other.
                  ;
                  duration / repeat /
                  ;
                  ; The following are OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  attach / x-prop / iana-prop
                  ;
                  )

   Description:  A "VALARM" calendar component is a grouping of
      component properties that is a reminder or alarm for an event or a
      to-do.  For example, it may be used to define a reminder for a
      pending event or an overdue to-do.

      The "VALARM" calendar component MUST include the "ACTION" and
      "TRIGGER" properties.  The "ACTION" property further constrains
      the "VALARM" calendar component in the following ways:

      When the action is "AUDIO", the alarm can also include one and
      only one "ATTACH" property, which MUST point to a sound resource,
      which is rendered when the alarm is triggered.

      When the action is "DISPLAY", the alarm MUST also include a
      "DESCRIPTION" property, which contains the text to be displayed
      when the alarm is triggered.

      When the action is "EMAIL", the alarm MUST include a "DESCRIPTION"
      property, which contains the text to be used as the message body,
      a "SUMMARY" property, which contains the text to be used as the
      message subject, and one or more "ATTENDEE" properties, which
      contain the email address of attendees to receive the message.  It
      can also include one or more "ATTACH" properties, which are
      intended to be sent as message attachments.  When the alarm is
      triggered, the email message is sent.

      The "VALARM" calendar component MUST only appear within either a
      "VEVENT" or "VTODO" calendar component.  "VALARM" calendar
      components cannot be nested.  Multiple mutually independent



Desruisseaux                Standards Track                    [Page 73]

RFC 5545                       iCalendar                  September 2009


      "VALARM" calendar components can be specified for a single
      "VEVENT" or "VTODO" calendar component.

      The "TRIGGER" property specifies when the alarm will be triggered.
      The "TRIGGER" property specifies a duration prior to the start of
      an event or a to-do.  The "TRIGGER" edge may be explicitly set to
      be relative to the "START" or "END" of the event or to-do with the
      "RELATED" parameter of the "TRIGGER" property.  The "TRIGGER"
      property value type can alternatively be set to an absolute
      calendar date with UTC time.

      In an alarm set to trigger on the "START" of an event or to-do,
      the "DTSTART" property MUST be present in the associated event or
      to-do.  In an alarm in a "VEVENT" calendar component set to
      trigger on the "END" of the event, either the "DTEND" property
      MUST be present, or the "DTSTART" and "DURATION" properties MUST
      both be present.  In an alarm in a "VTODO" calendar component set
      to trigger on the "END" of the to-do, either the "DUE" property
      MUST be present, or the "DTSTART" and "DURATION" properties MUST
      both be present.

      The alarm can be defined such that it triggers repeatedly.  A
      definition of an alarm with a repeating trigger MUST include both
      the "DURATION" and "REPEAT" properties.  The "DURATION" property
      specifies the delay period, after which the alarm will repeat.
      The "REPEAT" property specifies the number of additional
      repetitions that the alarm will be triggered.  This repetition
      count is in addition to the initial triggering of the alarm.  Both
      of these properties MUST be present in order to specify a
      repeating alarm.  If one of these two properties is absent, then
      the alarm will not repeat beyond the initial trigger.

      The "ACTION" property is used within the "VALARM" calendar
      component to specify the type of action invoked when the alarm is
      triggered.  The "VALARM" properties provide enough information for
      a specific action to be invoked.  It is typically the
      responsibility of a "Calendar User Agent" (CUA) to deliver the
      alarm in the specified fashion.  An "ACTION" property value of
      AUDIO specifies an alarm that causes a sound to be played to alert
      the user; DISPLAY specifies an alarm that causes a text message to
      be displayed to the user; and EMAIL specifies an alarm that causes
      an electronic email message to be delivered to one or more email
      addresses.

      In an AUDIO alarm, if the optional "ATTACH" property is included,
      it MUST specify an audio sound resource.  The intention is that
      the sound will be played as the alarm effect.  If an "ATTACH"
      property is specified that does not refer to a sound resource, or



Desruisseaux                Standards Track                    [Page 74]

RFC 5545                       iCalendar                  September 2009


      if the specified sound resource cannot be rendered (because its
      format is unsupported, or because it cannot be retrieved), then
      the CUA or other entity responsible for playing the sound may
      choose a fallback action, such as playing a built-in default
      sound, or playing no sound at all.

      In a DISPLAY alarm, the intended alarm effect is for the text
      value of the "DESCRIPTION" property to be displayed to the user.

      In an EMAIL alarm, the intended alarm effect is for an email
      message to be composed and delivered to all the addresses
      specified by the "ATTENDEE" properties in the "VALARM" calendar
      component.  The "DESCRIPTION" property of the "VALARM" calendar
      component MUST be used as the body text of the message, and the
      "SUMMARY" property MUST be used as the subject text.  Any "ATTACH"
      properties in the "VALARM" calendar component SHOULD be sent as
      attachments to the message.

         Note: Implementations should carefully consider whether they
         accept alarm components from untrusted sources, e.g., when
         importing calendar objects from external sources.  One
         reasonable policy is to always ignore alarm components that the
         calendar user has not set herself, or at least ask for
         confirmation in such a case.

   Example:  The following example is for a "VALARM" calendar component
      that specifies an audio alarm that will sound at a precise time
      and repeat 4 more times at 15-minute intervals:

       BEGIN:VALARM
       TRIGGER;VALUE=DATE-TIME:19970317T133000Z
       REPEAT:4
       DURATION:PT15M
       ACTION:AUDIO
       ATTACH;FMTTYPE=audio/basic:ftp://example.com/pub/
        sounds/bell-01.aud
       END:VALARM

      The following example is for a "VALARM" calendar component that
      specifies a display alarm that will trigger 30 minutes before the
      scheduled start of the event or of the to-do it is associated with
      and will repeat 2 more times at 15-minute intervals:









Desruisseaux                Standards Track                    [Page 75]

RFC 5545                       iCalendar                  September 2009


       BEGIN:VALARM
       TRIGGER:-PT30M
       REPEAT:2
       DURATION:PT15M
       ACTION:DISPLAY
       DESCRIPTION:Breakfast meeting with executive\n
        team at 8:30 AM EST.
       END:VALARM

      The following example is for a "VALARM" calendar component that
      specifies an email alarm that will trigger 2 days before the
      scheduled due DATE-TIME of a to-do with which it is associated.
      It does not repeat.  The email has a subject, body, and attachment
      link.

       BEGIN:VALARM
       TRIGGER;RELATED=END:-P2D
       ACTION:EMAIL
       ATTENDEE:mailto:john_doe@example.com
       SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
       DESCRIPTION:A draft agenda needs to be sent out to the attendees
         to the weekly managers meeting (MGR-LIST). Attached is a
         pointer the document template for the agenda file.
       ATTACH;FMTTYPE=application/msword:http://example.com/
        templates/agenda.doc
       END:VALARM

3.7.  Calendar Properties

   The Calendar Properties are attributes that apply to the iCalendar
   object, as a whole.  These properties do not appear within a calendar
   component.  They SHOULD be specified after the "BEGIN:VCALENDAR"
   delimiter string and prior to any calendar component.

3.7.1.  Calendar Scale

   Property Name:  CALSCALE

   Purpose:  This property defines the calendar scale used for the
      calendar information specified in the iCalendar object.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified once in an iCalendar
      object.  The default value is "GREGORIAN".



Desruisseaux                Standards Track                    [Page 76]

RFC 5545                       iCalendar                  September 2009


   Description:  This memo is based on the Gregorian calendar scale.
      The Gregorian calendar scale is assumed if this property is not
      specified in the iCalendar object.  It is expected that other
      calendar scales will be defined in other specifications or by
      future versions of this memo.

   Format Definition:  This property is defined by the following
      notation:

       calscale   = "CALSCALE" calparam ":" calvalue CRLF

       calparam   = *(";" other-param)

       calvalue   = "GREGORIAN"

   Example:  The following is an example of this property:

       CALSCALE:GREGORIAN

3.7.2.  Method

   Property Name:  METHOD

   Purpose:  This property defines the iCalendar object method
      associated with the calendar object.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified once in an iCalendar
      object.

   Description:  When used in a MIME message entity, the value of this
      property MUST be the same as the Content-Type "method" parameter
      value.  If either the "METHOD" property or the Content-Type
      "method" parameter is specified, then the other MUST also be
      specified.

      No methods are defined by this specification.  This is the subject
      of other specifications, such as the iCalendar Transport-
      independent Interoperability Protocol (iTIP) defined by [2446bis].

      If this property is not present in the iCalendar object, then a
      scheduling transaction MUST NOT be assumed.  In such cases, the
      iCalendar object is merely being used to transport a snapshot of




Desruisseaux                Standards Track                    [Page 77]

RFC 5545                       iCalendar                  September 2009


      some calendar information; without the intention of conveying a
      scheduling semantic.

   Format Definition:  This property is defined by the following
      notation:

       method     = "METHOD" metparam ":" metvalue CRLF

       metparam   = *(";" other-param)

       metvalue   = iana-token

   Example:  The following is a hypothetical example of this property to
      convey that the iCalendar object is a scheduling request:

       METHOD:REQUEST

3.7.3.  Product Identifier

   Property Name:  PRODID

   Purpose:  This property specifies the identifier for the product that
      created the iCalendar object.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  The property MUST be specified once in an iCalendar
      object.

   Description:  The vendor of the implementation SHOULD assure that
      this is a globally unique identifier; using some technique such as
      an FPI value, as defined in [ISO.9070.1991].

      This property SHOULD NOT be used to alter the interpretation of an
      iCalendar object beyond the semantics specified in this memo.  For
      example, it is not to be used to further the understanding of non-
      standard properties.

   Format Definition:  This property is defined by the following
      notation:

       prodid     = "PRODID" pidparam ":" pidvalue CRLF

       pidparam   = *(";" other-param)




Desruisseaux                Standards Track                    [Page 78]

RFC 5545                       iCalendar                  September 2009


       pidvalue   = text
       ;Any text that describes the product and version
       ;and that is generally assured of being unique.

   Example:  The following is an example of this property.  It does not
      imply that English is the default language.

       PRODID:-//ABC Corporation//NONSGML My Product//EN

3.7.4.  Version

   Property Name:  VERSION

   Purpose:  This property specifies the identifier corresponding to the
      highest version number or the minimum and maximum range of the
      iCalendar specification that is required in order to interpret the
      iCalendar object.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be specified once in an iCalendar
      object.

   Description:  A value of "2.0" corresponds to this memo.

   Format Definition:  This property is defined by the following
      notation:

       version    = "VERSION" verparam ":" vervalue CRLF

       verparam   = *(";" other-param)

       vervalue   = "2.0"         ;This memo
                  / maxver
                  / (minver ";" maxver)

       minver     = <A IANA-registered iCalendar version identifier>
       ;Minimum iCalendar version needed to parse the iCalendar object.

       maxver     = <A IANA-registered iCalendar version identifier>
       ;Maximum iCalendar version needed to parse the iCalendar object.







Desruisseaux                Standards Track                    [Page 79]

RFC 5545                       iCalendar                  September 2009


   Example:  The following is an example of this property:

       VERSION:2.0

3.8.  Component Properties

   The following properties can appear within calendar components, as
   specified by each component property definition.

3.8.1.  Descriptive Component Properties

   The following properties specify descriptive information about
   calendar components.

3.8.1.1.  Attachment

   Property Name:  ATTACH

   Purpose:  This property provides the capability to associate a
      document object with a calendar component.

   Value Type:  The default value type for this property is URI.  The
      value type can also be set to BINARY to indicate inline binary
      encoded content information.

   Property Parameters:  IANA, non-standard, inline encoding, and value
      data type property parameters can be specified on this property.
      The format type parameter can be specified on this property and is
      RECOMMENDED for inline binary encoded content information.

   Conformance:  This property can be specified multiple times in a
      "VEVENT", "VTODO", "VJOURNAL", or "VALARM" calendar component with
      the exception of AUDIO alarm that only allows this property to
      occur once.

   Description:  This property is used in "VEVENT", "VTODO", and
      "VJOURNAL" calendar components to associate a resource (e.g.,
      document) with the calendar component.  This property is used in
      "VALARM" calendar components to specify an audio sound resource or
      an email message attachment.  This property can be specified as a
      URI pointing to a resource or as inline binary encoded content.

      When this property is specified as inline binary encoded content,
      calendar applications MAY attempt to guess the media type of the
      resource via inspection of its content if and only if the media
      type of the resource is not given by the "FMTTYPE" parameter.  If
      the media type remains unknown, calendar applications SHOULD treat
      it as type "application/octet-stream".



Desruisseaux                Standards Track                    [Page 80]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This property is defined by the following
      notation:

       attach     = "ATTACH" attachparam ( ":" uri ) /
                    (
                      ";" "ENCODING" "=" "BASE64"
                      ";" "VALUE" "=" "BINARY"
                      ":" binary
                    )
                    CRLF

       attachparam = *(
                   ;
                   ; The following is OPTIONAL for a URI value,
                   ; RECOMMENDED for a BINARY value,
                   ; and MUST NOT occur more than once.
                   ;
                   (";" fmttypeparam) /
                   ;
                   ; The following is OPTIONAL,
                   ; and MAY occur more than once.
                   ;
                   (";" other-param)
                   ;
                   )

   Example:  The following are examples of this property:

       ATTACH:CID:jsmith.part3.960817T083000.xyzMail@example.com

       ATTACH;FMTTYPE=application/postscript:ftp://example.com/pub/
        reports/r-960812.ps

3.8.1.2.  Categories

   Property Name:  CATEGORIES

   Purpose:  This property defines the categories for a calendar
      component.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, and language property
      parameters can be specified on this property.

   Conformance:  The property can be specified within "VEVENT", "VTODO",
      or "VJOURNAL" calendar components.




Desruisseaux                Standards Track                    [Page 81]

RFC 5545                       iCalendar                  September 2009


   Description:  This property is used to specify categories or subtypes
      of the calendar component.  The categories are useful in searching
      for a calendar component of a particular type and category.
      Within the "VEVENT", "VTODO", or "VJOURNAL" calendar components,
      more than one category can be specified as a COMMA-separated list
      of categories.

   Format Definition:  This property is defined by the following
      notation:

       categories = "CATEGORIES" catparam ":" text *("," text)
                    CRLF

       catparam   = *(
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" languageparam ) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following are examples of this property:

       CATEGORIES:APPOINTMENT,EDUCATION

       CATEGORIES:MEETING

3.8.1.3.  Classification

   Property Name:  CLASS

   Purpose:  This property defines the access classification for a
      calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  The property can be specified once in a "VEVENT",
      "VTODO", or "VJOURNAL" calendar components.




Desruisseaux                Standards Track                    [Page 82]

RFC 5545                       iCalendar                  September 2009


   Description:  An access classification is only one component of the
      general security system within a calendar application.  It
      provides a method of capturing the scope of the access the
      calendar owner intends for information within an individual
      calendar entry.  The access classification of an individual
      iCalendar component is useful when measured along with the other
      security components of a calendar system (e.g., calendar user
      authentication, authorization, access rights, access role, etc.).
      Hence, the semantics of the individual access classifications
      cannot be completely defined by this memo alone.  Additionally,
      due to the "blind" nature of most exchange processes using this
      memo, these access classifications cannot serve as an enforcement
      statement for a system receiving an iCalendar object.  Rather,
      they provide a method for capturing the intention of the calendar
      owner for the access to the calendar component.  If not specified
      in a component that allows this property, the default value is
      PUBLIC.  Applications MUST treat x-name and iana-token values they
      don't recognize the same way as they would the PRIVATE value.

   Format Definition:  This property is defined by the following
      notation:

       class      = "CLASS" classparam ":" classvalue CRLF

       classparam = *(";" other-param)

       classvalue = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL" / iana-token
                  / x-name
       ;Default is PUBLIC

   Example:  The following is an example of this property:

       CLASS:PUBLIC

3.8.1.4.  Comment

   Property Name:  COMMENT

   Purpose:  This property specifies non-processing information intended
      to provide a comment to the calendar user.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, alternate text
      representation, and language property parameters can be specified
      on this property.





Desruisseaux                Standards Track                    [Page 83]

RFC 5545                       iCalendar                  September 2009


   Conformance:  This property can be specified multiple times in
      "VEVENT", "VTODO", "VJOURNAL", and "VFREEBUSY" calendar components
      as well as in the "STANDARD" and "DAYLIGHT" sub-components.

   Description:  This property is used to specify a comment to the
      calendar user.

   Format Definition:  This property is defined by the following
      notation:

       comment    = "COMMENT" commparam ":" text CRLF

       commparam  = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" altrepparam) / (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following is an example of this property:

       COMMENT:The meeting really needs to include both ourselves
         and the customer. We can't hold this meeting without them.
         As a matter of fact\, the venue for the meeting ought to be at
         their site. - - John

3.8.1.5.  Description

   Property Name:  DESCRIPTION

   Purpose:  This property provides a more complete description of the
      calendar component than that provided by the "SUMMARY" property.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, alternate text
      representation, and language property parameters can be specified
      on this property.






Desruisseaux                Standards Track                    [Page 84]

RFC 5545                       iCalendar                  September 2009


   Conformance:  The property can be specified in the "VEVENT", "VTODO",
      "VJOURNAL", or "VALARM" calendar components.  The property can be
      specified multiple times only within a "VJOURNAL" calendar
      component.

   Description:  This property is used in the "VEVENT" and "VTODO" to
      capture lengthy textual descriptions associated with the activity.

      This property is used in the "VJOURNAL" calendar component to
      capture one or more textual journal entries.

      This property is used in the "VALARM" calendar component to
      capture the display text for a DISPLAY category of alarm, and to
      capture the body text for an EMAIL category of alarm.

   Format Definition:  This property is defined by the following
      notation:

       description = "DESCRIPTION" descparam ":" text CRLF

       descparam   = *(
                   ;
                   ; The following are OPTIONAL,
                   ; but MUST NOT occur more than once.
                   ;
                   (";" altrepparam) / (";" languageparam) /
                   ;
                   ; The following is OPTIONAL,
                   ; and MAY occur more than once.
                   ;
                   (";" other-param)
                   ;
                   )

   Example:  The following is an example of this property with formatted
      line breaks in the property value:

       DESCRIPTION:Meeting to provide technical review for "Phoenix"
         design.\nHappy Face Conference Room. Phoenix design team
         MUST attend this meeting.\nRSVP to team leader.

3.8.1.6.  Geographic Position

   Property Name:  GEO

   Purpose:  This property specifies information related to the global
      position for the activity specified by a calendar component.




Desruisseaux                Standards Track                    [Page 85]

RFC 5545                       iCalendar                  September 2009


   Value Type:  FLOAT.  The value MUST be two SEMICOLON-separated FLOAT
      values.

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in "VEVENT" or "VTODO"
      calendar components.

   Description:  This property value specifies latitude and longitude,
      in that order (i.e., "LAT LON" ordering).  The longitude
      represents the location east or west of the prime meridian as a
      positive or negative real number, respectively.  The longitude and
      latitude values MAY be specified up to six decimal places, which
      will allow for accuracy to within one meter of geographical
      position.  Receiving applications MUST accept values of this
      precision and MAY truncate values of greater precision.

      Values for latitude and longitude shall be expressed as decimal
      fractions of degrees.  Whole degrees of latitude shall be
      represented by a two-digit decimal number ranging from 0 through
      90.  Whole degrees of longitude shall be represented by a decimal
      number ranging from 0 through 180.  When a decimal fraction of a
      degree is specified, it shall be separated from the whole number
      of degrees by a decimal point.

      Latitudes north of the equator shall be specified by a plus sign
      (+), or by the absence of a minus sign (-), preceding the digits
      designating degrees.  Latitudes south of the Equator shall be
      designated by a minus sign (-) preceding the digits designating
      degrees.  A point on the Equator shall be assigned to the Northern
      Hemisphere.

      Longitudes east of the prime meridian shall be specified by a plus
      sign (+), or by the absence of a minus sign (-), preceding the
      digits designating degrees.  Longitudes west of the meridian shall
      be designated by minus sign (-) preceding the digits designating
      degrees.  A point on the prime meridian shall be assigned to the
      Eastern Hemisphere.  A point on the 180th meridian shall be
      assigned to the Western Hemisphere.  One exception to this last
      convention is permitted.  For the special condition of describing
      a band of latitude around the earth, the East Bounding Coordinate
      data element shall be assigned the value +180 (180) degrees.

      Any spatial address with a latitude of +90 (90) or -90 degrees
      will specify the position at the North or South Pole,
      respectively.  The component for longitude may have any legal
      value.



Desruisseaux                Standards Track                    [Page 86]

RFC 5545                       iCalendar                  September 2009


      With the exception of the special condition described above, this
      form is specified in [ANSI INCITS 61-1986].

      The simple formula for converting degrees-minutes-seconds into
      decimal degrees is:

      decimal = degrees + minutes/60 + seconds/3600.

   Format Definition:  This property is defined by the following
      notation:

       geo        = "GEO" geoparam ":" geovalue CRLF

       geoparam   = *(";" other-param)

       geovalue   = float ";" float
       ;Latitude and Longitude components

   Example:  The following is an example of this property:

       GEO:37.386013;-122.082932

3.8.1.7.  Location

   Property Name:  LOCATION

   Purpose:  This property defines the intended venue for the activity
      defined by a calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, alternate text
      representation, and language property parameters can be specified
      on this property.

   Conformance:  This property can be specified in "VEVENT" or "VTODO"
      calendar component.

   Description:  Specific venues such as conference or meeting rooms may
      be explicitly specified using this property.  An alternate
      representation may be specified that is a URI that points to
      directory information with more structured specification of the
      location.  For example, the alternate representation may specify
      either an LDAP URL [RFC4516] pointing to an LDAP server entry or a
      CID URL [RFC2392] pointing to a MIME body part containing a
      Virtual-Information Card (vCard) [RFC2426] for the location.





Desruisseaux                Standards Track                    [Page 87]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This property is defined by the following
      notation:

       location   = "LOCATION"  locparam ":" text CRLF

       locparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" altrepparam) / (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following are some examples of this property:

       LOCATION:Conference Room - F123\, Bldg. 002

       LOCATION;ALTREP="http://xyzcorp.com/conf-rooms/f123.vcf":
        Conference Room - F123\, Bldg. 002

3.8.1.8.  Percent Complete

   Property Name:  PERCENT-COMPLETE

   Purpose:  This property is used by an assignee or delegatee of a
      to-do to convey the percent completion of a to-do to the
      "Organizer".

   Value Type:  INTEGER

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified once in a "VTODO"
      calendar component.

   Description:  The property value is a positive integer between 0 and
      100.  A value of "0" indicates the to-do has not yet been started.
      A value of "100" indicates that the to-do has been completed.
      Integer values in between indicate the percent partially complete.





Desruisseaux                Standards Track                    [Page 88]

RFC 5545                       iCalendar                  September 2009


      When a to-do is assigned to multiple individuals, the property
      value indicates the percent complete for that portion of the to-do
      assigned to the assignee or delegatee.  For example, if a to-do is
      assigned to both individuals "A" and "B".  A reply from "A" with a
      percent complete of "70" indicates that "A" has completed 70% of
      the to-do assigned to them.  A reply from "B" with a percent
      complete of "50" indicates "B" has completed 50% of the to-do
      assigned to them.

   Format Definition:  This property is defined by the following
      notation:

       percent = "PERCENT-COMPLETE" pctparam ":" integer CRLF

       pctparam   = *(";" other-param)

   Example:  The following is an example of this property to show 39%
      completion:

       PERCENT-COMPLETE:39

3.8.1.9.  Priority

   Property Name:  PRIORITY

   Purpose:  This property defines the relative priority for a calendar
      component.

   Value Type:  INTEGER

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in "VEVENT" and "VTODO"
      calendar components.

   Description:  This priority is specified as an integer in the range 0
      to 9.  A value of 0 specifies an undefined priority.  A value of 1
      is the highest priority.  A value of 2 is the second highest
      priority.  Subsequent numbers specify a decreasing ordinal
      priority.  A value of 9 is the lowest priority.

      A CUA with a three-level priority scheme of "HIGH", "MEDIUM", and
      "LOW" is mapped into this property such that a property value in
      the range of 1 to 4 specifies "HIGH" priority.  A value of 5 is
      the normal or "MEDIUM" priority.  A value in the range of 6 to 9
      is "LOW" priority.




Desruisseaux                Standards Track                    [Page 89]

RFC 5545                       iCalendar                  September 2009


      A CUA with a priority schema of "A1", "A2", "A3", "B1", "B2", ...,
      "C3" is mapped into this property such that a property value of 1
      specifies "A1", a property value of 2 specifies "A2", a property
      value of 3 specifies "A3", and so forth up to a property value of
      9 specifies "C3".

      Other integer values are reserved for future use.

      Within a "VEVENT" calendar component, this property specifies a
      priority for the event.  This property may be useful when more
      than one event is scheduled for a given time period.

      Within a "VTODO" calendar component, this property specified a
      priority for the to-do.  This property is useful in prioritizing
      multiple action items for a given time period.

   Format Definition:  This property is defined by the following
      notation:

       priority   = "PRIORITY" prioparam ":" priovalue CRLF
       ;Default is zero (i.e., undefined).

       prioparam  = *(";" other-param)

       priovalue   = integer       ;Must be in the range [0..9]
          ; All other values are reserved for future use.

   Example:  The following is an example of a property with the highest
      priority:

       PRIORITY:1

      The following is an example of a property with a next highest
      priority:

       PRIORITY:2

      The following is an example of a property with no priority.  This
      is equivalent to not specifying the "PRIORITY" property:

       PRIORITY:0










Desruisseaux                Standards Track                    [Page 90]

RFC 5545                       iCalendar                  September 2009


3.8.1.10.  Resources

   Property Name:  RESOURCES

   Purpose:  This property defines the equipment or resources
      anticipated for an activity specified by a calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, alternate text
      representation, and language property parameters can be specified
      on this property.

   Conformance:  This property can be specified once in "VEVENT" or
      "VTODO" calendar component.

   Description:  The property value is an arbitrary text.  More than one
      resource can be specified as a COMMA-separated list of resources.

   Format Definition:  This property is defined by the following
      notation:

       resources  = "RESOURCES" resrcparam ":" text *("," text) CRLF

       resrcparam = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" altrepparam) / (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following is an example of this property:

       RESOURCES:EASEL,PROJECTOR,VCR

       RESOURCES;LANGUAGE=fr:Nettoyeur haute pression








Desruisseaux                Standards Track                    [Page 91]

RFC 5545                       iCalendar                  September 2009


3.8.1.11.  Status

   Property Name:  STATUS

   Purpose:  This property defines the overall status or confirmation
      for the calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified once in "VEVENT",
      "VTODO", or "VJOURNAL" calendar components.

   Description:  In a group-scheduled calendar component, the property
      is used by the "Organizer" to provide a confirmation of the event
      to the "Attendees".  For example in a "VEVENT" calendar component,
      the "Organizer" can indicate that a meeting is tentative,
      confirmed, or cancelled.  In a "VTODO" calendar component, the
      "Organizer" can indicate that an action item needs action, is
      completed, is in process or being worked on, or has been
      cancelled.  In a "VJOURNAL" calendar component, the "Organizer"
      can indicate that a journal entry is draft, final, or has been
      cancelled or removed.

   Format Definition:  This property is defined by the following
      notation:

       status          = "STATUS" statparam ":" statvalue CRLF

       statparam       = *(";" other-param)

       statvalue       = (statvalue-event
                       /  statvalue-todo
                       /  statvalue-jour)

       statvalue-event = "TENTATIVE"    ;Indicates event is tentative.
                       / "CONFIRMED"    ;Indicates event is definite.
                       / "CANCELLED"    ;Indicates event was cancelled.
       ;Status values for a "VEVENT"

       statvalue-todo  = "NEEDS-ACTION" ;Indicates to-do needs action.
                       / "COMPLETED"    ;Indicates to-do completed.
                       / "IN-PROCESS"   ;Indicates to-do in process of.
                       / "CANCELLED"    ;Indicates to-do was cancelled.
       ;Status values for "VTODO".




Desruisseaux                Standards Track                    [Page 92]

RFC 5545                       iCalendar                  September 2009


       statvalue-jour  = "DRAFT"        ;Indicates journal is draft.
                       / "FINAL"        ;Indicates journal is final.
                       / "CANCELLED"    ;Indicates journal is removed.
      ;Status values for "VJOURNAL".

   Example:  The following is an example of this property for a "VEVENT"
      calendar component:

       STATUS:TENTATIVE

      The following is an example of this property for a "VTODO"
      calendar component:

       STATUS:NEEDS-ACTION

      The following is an example of this property for a "VJOURNAL"
      calendar component:

       STATUS:DRAFT

3.8.1.12.  Summary

   Property Name:  SUMMARY

   Purpose:  This property defines a short summary or subject for the
      calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, alternate text
      representation, and language property parameters can be specified
      on this property.

   Conformance:  The property can be specified in "VEVENT", "VTODO",
      "VJOURNAL", or "VALARM" calendar components.

   Description:  This property is used in the "VEVENT", "VTODO", and
      "VJOURNAL" calendar components to capture a short, one-line
      summary about the activity or journal entry.

      This property is used in the "VALARM" calendar component to
      capture the subject of an EMAIL category of alarm.

   Format Definition:  This property is defined by the following
      notation:






Desruisseaux                Standards Track                    [Page 93]

RFC 5545                       iCalendar                  September 2009


       summary    = "SUMMARY" summparam ":" text CRLF

       summparam  = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" altrepparam) / (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following is an example of this property:

       SUMMARY:Department Party

3.8.2.  Date and Time Component Properties

   The following properties specify date and time related information in
   calendar components.

3.8.2.1.  Date-Time Completed

   Property Name:  COMPLETED

   Purpose:  This property defines the date and time that a to-do was
      actually completed.

   Value Type:  DATE-TIME

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  The property can be specified in a "VTODO" calendar
      component.  The value MUST be specified as a date with UTC time.

   Description:  This property defines the date and time that a to-do
      was actually completed.

   Format Definition:  This property is defined by the following
      notation:






Desruisseaux                Standards Track                    [Page 94]

RFC 5545                       iCalendar                  September 2009


       completed  = "COMPLETED" compparam ":" date-time CRLF

       compparam  = *(";" other-param)

   Example:  The following is an example of this property:

    COMPLETED:19960401T150000Z

3.8.2.2.  Date-Time End

   Property Name:  DTEND

   Purpose:  This property specifies the date and time that a calendar
      component ends.

   Value Type:  The default value type is DATE-TIME.  The value type can
      be set to a DATE value type.

   Property Parameters:  IANA, non-standard, value data type, and time
      zone identifier property parameters can be specified on this
      property.

   Conformance:  This property can be specified in "VEVENT" or
      "VFREEBUSY" calendar components.

   Description:  Within the "VEVENT" calendar component, this property
      defines the date and time by which the event ends.  The value type
      of this property MUST be the same as the "DTSTART" property, and
      its value MUST be later in time than the value of the "DTSTART"
      property.  Furthermore, this property MUST be specified as a date
      with local time if and only if the "DTSTART" property is also
      specified as a date with local time.

      Within the "VFREEBUSY" calendar component, this property defines
      the end date and time for the free or busy time information.  The
      time MUST be specified in the UTC time format.  The value MUST be
      later in time than the value of the "DTSTART" property.

   Format Definition:  This property is defined by the following
      notation:











Desruisseaux                Standards Track                    [Page 95]

RFC 5545                       iCalendar                  September 2009


       dtend      = "DTEND" dtendparam ":" dtendval CRLF

       dtendparam = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  (";" tzidparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       dtendval   = date-time / date
       ;Value MUST match value type

   Example:  The following is an example of this property:

       DTEND:19960401T150000Z

       DTEND;VALUE=DATE:19980704

3.8.2.3.  Date-Time Due

   Property Name:  DUE

   Purpose:  This property defines the date and time that a to-do is
      expected to be completed.

   Value Type:  The default value type is DATE-TIME.  The value type can
      be set to a DATE value type.

   Property Parameters:  IANA, non-standard, value data type, and time
      zone identifier property parameters can be specified on this
      property.

   Conformance:  The property can be specified once in a "VTODO"
      calendar component.

   Description:  This property defines the date and time before which a
      to-do is expected to be completed.  For cases where this property
      is specified in a "VTODO" calendar component that also specifies a
      "DTSTART" property, the value type of this property MUST be the
      same as the "DTSTART" property, and the value of this property



Desruisseaux                Standards Track                    [Page 96]

RFC 5545                       iCalendar                  September 2009


      MUST be later in time than the value of the "DTSTART" property.
      Furthermore, this property MUST be specified as a date with local
      time if and only if the "DTSTART" property is also specified as a
      date with local time.

   Format Definition:  This property is defined by the following
      notation:

       due        = "DUE" dueparam ":" dueval CRLF

       dueparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  (";" tzidparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       dueval     = date-time / date
       ;Value MUST match value type

   Example:  The following is an example of this property:

       DUE:19980430T000000Z

3.8.2.4.  Date-Time Start

   Property Name:  DTSTART

   Purpose:  This property specifies when the calendar component begins.

   Value Type:  The default value type is DATE-TIME.  The time value
      MUST be one of the forms defined for the DATE-TIME value type.
      The value type can be set to a DATE value type.

   Property Parameters:  IANA, non-standard, value data type, and time
      zone identifier property parameters can be specified on this
      property.

   Conformance:  This property can be specified once in the "VEVENT",
      "VTODO", or "VFREEBUSY" calendar components as well as in the



Desruisseaux                Standards Track                    [Page 97]

RFC 5545                       iCalendar                  September 2009


      "STANDARD" and "DAYLIGHT" sub-components.  This property is
      REQUIRED in all types of recurring calendar components that
      specify the "RRULE" property.  This property is also REQUIRED in
      "VEVENT" calendar components contained in iCalendar objects that
      don't specify the "METHOD" property.

   Description:  Within the "VEVENT" calendar component, this property
      defines the start date and time for the event.

      Within the "VFREEBUSY" calendar component, this property defines
      the start date and time for the free or busy time information.
      The time MUST be specified in UTC time.

      Within the "STANDARD" and "DAYLIGHT" sub-components, this property
      defines the effective start date and time for a time zone
      specification.  This property is REQUIRED within each "STANDARD"
      and "DAYLIGHT" sub-components included in "VTIMEZONE" calendar
      components and MUST be specified as a date with local time without
      the "TZID" property parameter.

   Format Definition:  This property is defined by the following
      notation:

       dtstart    = "DTSTART" dtstparam ":" dtstval CRLF

       dtstparam  = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  (";" tzidparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       dtstval    = date-time / date
       ;Value MUST match value type

   Example:  The following is an example of this property:

       DTSTART:19980118T073000Z





Desruisseaux                Standards Track                    [Page 98]

RFC 5545                       iCalendar                  September 2009


3.8.2.5.  Duration

   Property Name:  DURATION

   Purpose:  This property specifies a positive duration of time.

   Value Type:  DURATION

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in "VEVENT", "VTODO", or
      "VALARM" calendar components.

   Description:  In a "VEVENT" calendar component the property may be
      used to specify a duration of the event, instead of an explicit
      end DATE-TIME.  In a "VTODO" calendar component the property may
      be used to specify a duration for the to-do, instead of an
      explicit due DATE-TIME.  In a "VALARM" calendar component the
      property may be used to specify the delay period prior to
      repeating an alarm.  When the "DURATION" property relates to a
      "DTSTART" property that is specified as a DATE value, then the
      "DURATION" property MUST be specified as a "dur-day" or "dur-week"
      value.

   Format Definition:  This property is defined by the following
      notation:

       duration   = "DURATION" durparam ":" dur-value CRLF
                    ;consisting of a positive duration of time.

       durparam   = *(";" other-param)

   Example:  The following is an example of this property that specifies
      an interval of time of one hour and zero minutes and zero seconds:

       DURATION:PT1H0M0S

      The following is an example of this property that specifies an
      interval of time of 15 minutes.

       DURATION:PT15M









Desruisseaux                Standards Track                    [Page 99]

RFC 5545                       iCalendar                  September 2009


3.8.2.6.  Free/Busy Time

   Property Name:  FREEBUSY

   Purpose:  This property defines one or more free or busy time
      intervals.

   Value Type:  PERIOD

   Property Parameters:  IANA, non-standard, and free/busy time type
      property parameters can be specified on this property.

   Conformance:  The property can be specified in a "VFREEBUSY" calendar
      component.

   Description:  These time periods can be specified as either a start
      and end DATE-TIME or a start DATE-TIME and DURATION.  The date and
      time MUST be a UTC time format.

      "FREEBUSY" properties within the "VFREEBUSY" calendar component
      SHOULD be sorted in ascending order, based on start time and then
      end time, with the earliest periods first.

      The "FREEBUSY" property can specify more than one value, separated
      by the COMMA character.  In such cases, the "FREEBUSY" property
      values MUST all be of the same "FBTYPE" property parameter type
      (e.g., all values of a particular "FBTYPE" listed together in a
      single property).

   Format Definition:  This property is defined by the following
      notation:

       freebusy   = "FREEBUSY" fbparam ":" fbvalue CRLF

       fbparam    = *(
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" fbtypeparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )




Desruisseaux                Standards Track                   [Page 100]

RFC 5545                       iCalendar                  September 2009


       fbvalue    = period *("," period)
       ;Time value MUST be in the UTC time format.

   Example:  The following are some examples of this property:

       FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:19970308T160000Z/PT8H30M

       FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H

       FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H
        ,19970308T230000Z/19970309T000000Z

3.8.2.7.  Time Transparency

   Property Name:  TRANSP

   Purpose:  This property defines whether or not an event is
      transparent to busy time searches.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified once in a "VEVENT"
      calendar component.

   Description:  Time Transparency is the characteristic of an event
      that determines whether it appears to consume time on a calendar.
      Events that consume actual time for the individual or resource
      associated with the calendar SHOULD be recorded as OPAQUE,
      allowing them to be detected by free/busy time searches.  Other
      events, which do not take up the individual's (or resource's) time
      SHOULD be recorded as TRANSPARENT, making them invisible to free/
      busy time searches.

   Format Definition:  This property is defined by the following
      notation:

       transp     = "TRANSP" transparam ":" transvalue CRLF

       transparam = *(";" other-param)

       transvalue = "OPAQUE"
                   ;Blocks or opaque on busy time searches.
                   / "TRANSPARENT"
                   ;Transparent on busy time searches.
       ;Default value is OPAQUE



Desruisseaux                Standards Track                   [Page 101]

RFC 5545                       iCalendar                  September 2009


   Example:  The following is an example of this property for an event
      that is transparent or does not block on free/busy time searches:

       TRANSP:TRANSPARENT

      The following is an example of this property for an event that is
      opaque or blocks on free/busy time searches:

       TRANSP:OPAQUE

3.8.3.  Time Zone Component Properties

   The following properties specify time zone information in calendar
   components.

3.8.3.1.  Time Zone Identifier

   Property Name:  TZID

   Purpose:  This property specifies the text value that uniquely
      identifies the "VTIMEZONE" calendar component in the scope of an
      iCalendar object.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be specified in a "VTIMEZONE"
      calendar component.

   Description:  This is the label by which a time zone calendar
      component is referenced by any iCalendar properties whose value
      type is either DATE-TIME or TIME and not intended to specify a UTC
      or a "floating" time.  The presence of the SOLIDUS character as a
      prefix, indicates that this "TZID" represents an unique ID in a
      globally defined time zone registry (when such registry is
      defined).

         Note: This document does not define a naming convention for
         time zone identifiers.  Implementers may want to use the naming
         conventions defined in existing time zone specifications such
         as the public-domain TZ database [TZDB].  The specification of
         globally unique time zone identifiers is not addressed by this
         document and is left for future study.






Desruisseaux                Standards Track                   [Page 102]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This property is defined by the following
      notation:

       tzid       = "TZID" tzidpropparam ":" [tzidprefix] text CRLF

       tzidpropparam      = *(";" other-param)

       ;tzidprefix        = "/"
       ; Defined previously. Just listed here for reader convenience.

   Example:  The following are examples of non-globally unique time zone
      identifiers:

       TZID:America/New_York

       TZID:America/Los_Angeles

      The following is an example of a fictitious globally unique time
      zone identifier:

       TZID:/example.org/America/New_York

3.8.3.2.  Time Zone Name

   Property Name:  TZNAME

   Purpose:  This property specifies the customary designation for a
      time zone description.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, and language property
      parameters can be specified on this property.

   Conformance:  This property can be specified in "STANDARD" and
      "DAYLIGHT" sub-components.

   Description:  This property specifies a customary name that can be
      used when displaying dates that occur during the observance
      defined by the time zone sub-component.

   Format Definition:  This property is defined by the following
      notation:








Desruisseaux                Standards Track                   [Page 103]

RFC 5545                       iCalendar                  September 2009


       tzname     = "TZNAME" tznparam ":" text CRLF

       tznparam   = *(
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following are examples of this property:

       TZNAME:EST

       TZNAME;LANGUAGE=fr-CA:HNE

3.8.3.3.  Time Zone Offset From

   Property Name:  TZOFFSETFROM

   Purpose:  This property specifies the offset that is in use prior to
      this time zone observance.

   Value Type:  UTC-OFFSET

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be specified in "STANDARD" and
      "DAYLIGHT" sub-components.

   Description:  This property specifies the offset that is in use prior
      to this time observance.  It is used to calculate the absolute
      time at which the transition to a given observance takes place.
      This property MUST only be specified in a "VTIMEZONE" calendar
      component.  A "VTIMEZONE" calendar component MUST include this
      property.  The property value is a signed numeric indicating the
      number of hours and possibly minutes from UTC.  Positive numbers
      represent time zones east of the prime meridian, or ahead of UTC.
      Negative numbers represent time zones west of the prime meridian,
      or behind UTC.




Desruisseaux                Standards Track                   [Page 104]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This property is defined by the following
      notation:

       tzoffsetfrom       = "TZOFFSETFROM" frmparam ":" utc-offset
                            CRLF

       frmparam   = *(";" other-param)

   Example:  The following are examples of this property:

       TZOFFSETFROM:-0500

       TZOFFSETFROM:+1345

3.8.3.4.  Time Zone Offset To

   Property Name:  TZOFFSETTO

   Purpose:  This property specifies the offset that is in use in this
      time zone observance.

   Value Type:  UTC-OFFSET

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be specified in "STANDARD" and
      "DAYLIGHT" sub-components.

   Description:  This property specifies the offset that is in use in
      this time zone observance.  It is used to calculate the absolute
      time for the new observance.  The property value is a signed
      numeric indicating the number of hours and possibly minutes from
      UTC.  Positive numbers represent time zones east of the prime
      meridian, or ahead of UTC.  Negative numbers represent time zones
      west of the prime meridian, or behind UTC.

   Format Definition:  This property is defined by the following
      notation:

       tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF

       toparam    = *(";" other-param)








Desruisseaux                Standards Track                   [Page 105]

RFC 5545                       iCalendar                  September 2009


   Example:  The following are examples of this property:

       TZOFFSETTO:-0400

       TZOFFSETTO:+1245

3.8.3.5.  Time Zone URL

   Property Name:  TZURL

   Purpose:  This property provides a means for a "VTIMEZONE" component
      to point to a network location that can be used to retrieve an up-
      to-date version of itself.

   Value Type:  URI

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in a "VTIMEZONE"
      calendar component.

   Description:  This property provides a means for a "VTIMEZONE"
      component to point to a network location that can be used to
      retrieve an up-to-date version of itself.  This provides a hook to
      handle changes government bodies impose upon time zone
      definitions.  Retrieval of this resource results in an iCalendar
      object containing a single "VTIMEZONE" component and a "METHOD"
      property set to PUBLISH.

   Format Definition:  This property is defined by the following
      notation:

       tzurl      = "TZURL" tzurlparam ":" uri CRLF

       tzurlparam = *(";" other-param)

   Example:  The following is an example of this property:

    TZURL:http://timezones.example.org/tz/America-Los_Angeles.ics

3.8.4.  Relationship Component Properties

   The following properties specify relationship information in calendar
   components.






Desruisseaux                Standards Track                   [Page 106]

RFC 5545                       iCalendar                  September 2009


3.8.4.1.  Attendee

   Property Name:  ATTENDEE

   Purpose:  This property defines an "Attendee" within a calendar
      component.

   Value Type:  CAL-ADDRESS

   Property Parameters:  IANA, non-standard, language, calendar user
      type, group or list membership, participation role, participation
      status, RSVP expectation, delegatee, delegator, sent by, common
      name, or directory entry reference property parameters can be
      specified on this property.

   Conformance:  This property MUST be specified in an iCalendar object
      that specifies a group-scheduled calendar entity.  This property
      MUST NOT be specified in an iCalendar object when publishing the
      calendar information (e.g., NOT in an iCalendar object that
      specifies the publication of a calendar user's busy time, event,
      to-do, or journal).  This property is not specified in an
      iCalendar object that specifies only a time zone definition or
      that defines calendar components that are not group-scheduled
      components, but are components only on a single user's calendar.

   Description:  This property MUST only be specified within calendar
      components to specify participants, non-participants, and the
      chair of a group-scheduled calendar entity.  The property is
      specified within an "EMAIL" category of the "VALARM" calendar
      component to specify an email address that is to receive the email
      type of iCalendar alarm.

      The property parameter "CN" is for the common or displayable name
      associated with the calendar address; "ROLE", for the intended
      role that the attendee will have in the calendar component;
      "PARTSTAT", for the status of the attendee's participation;
      "RSVP", for indicating whether the favor of a reply is requested;
      "CUTYPE", to indicate the type of calendar user; "MEMBER", to
      indicate the groups that the attendee belongs to; "DELEGATED-TO",
      to indicate the calendar users that the original request was
      delegated to; and "DELEGATED-FROM", to indicate whom the request
      was delegated from; "SENT-BY", to indicate whom is acting on
      behalf of the "ATTENDEE"; and "DIR", to indicate the URI that
      points to the directory information corresponding to the attendee.
      These property parameters can be specified on an "ATTENDEE"
      property in either a "VEVENT", "VTODO", or "VJOURNAL" calendar
      component.  They MUST NOT be specified in an "ATTENDEE" property
      in a "VFREEBUSY" or "VALARM" calendar component.  If the



Desruisseaux                Standards Track                   [Page 107]

RFC 5545                       iCalendar                  September 2009


      "LANGUAGE" property parameter is specified, the identified
      language applies to the "CN" parameter.

      A recipient delegated a request MUST inherit the "RSVP" and "ROLE"
      values from the attendee that delegated the request to them.

      Multiple attendees can be specified by including multiple
      "ATTENDEE" properties within the calendar component.

   Format Definition:  This property is defined by the following
      notation:

       attendee   = "ATTENDEE" attparam ":" cal-address CRLF

       attparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" cutypeparam) / (";" memberparam) /
                  (";" roleparam) / (";" partstatparam) /
                  (";" rsvpparam) / (";" deltoparam) /
                  (";" delfromparam) / (";" sentbyparam) /
                  (";" cnparam) / (";" dirparam) /
                  (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following are examples of this property's use for a
      to-do:

       ATTENDEE;MEMBER="mailto:DEV-GROUP@example.com":
        mailto:joecool@example.com
       ATTENDEE;DELEGATED-FROM="mailto:immud@example.com":
        mailto:ildoit@example.com











Desruisseaux                Standards Track                   [Page 108]

RFC 5545                       iCalendar                  September 2009


      The following is an example of this property used for specifying
      multiple attendees to an event:

       ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry
        Cabot:mailto:hcabot@example.com
       ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM="mailto:bob@
        example.com";PARTSTAT=ACCEPTED;CN=Jane Doe:mailto:jdoe@
        example.com

      The following is an example of this property with a URI to the
      directory information associated with the attendee:

       ATTENDEE;CN=John Smith;DIR="ldap://example.com:6666/o=ABC%
        20Industries,c=US???(cn=Jim%20Dolittle)":mailto:jimdo@
        example.com

      The following is an example of this property with "delegatee" and
      "delegator" information for an event:

       ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
        "mailto:iamboss@example.com";CN=Henry Cabot:mailto:hcabot@
        example.com
       ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
        "mailto:hcabot@example.com";CN=The Big Cheese:mailto:iamboss
        @example.com
       ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
        :mailto:jdoe@example.com

   Example:  The following is an example of this property's use when
      another calendar user is acting on behalf of the "Attendee":

       ATTENDEE;SENT-BY=mailto:jan_doe@example.com;CN=John Smith:
        mailto:jsmith@example.com

3.8.4.2.  Contact

   Property Name:  CONTACT

   Purpose:  This property is used to represent contact information or
      alternately a reference to contact information associated with the
      calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, alternate text
      representation, and language property parameters can be specified
      on this property.




Desruisseaux                Standards Track                   [Page 109]

RFC 5545                       iCalendar                  September 2009


   Conformance:  This property can be specified in a "VEVENT", "VTODO",
      "VJOURNAL", or "VFREEBUSY" calendar component.

   Description:  The property value consists of textual contact
      information.  An alternative representation for the property value
      can also be specified that refers to a URI pointing to an
      alternate form, such as a vCard [RFC2426], for the contact
      information.

   Format Definition:  This property is defined by the following
      notation:

       contact    = "CONTACT" contparam ":" text CRLF

       contparam  = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" altrepparam) / (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following is an example of this property referencing
      textual contact information:

       CONTACT:Jim Dolittle\, ABC Industries\, +1-919-555-1234

      The following is an example of this property with an alternate
      representation of an LDAP URI to a directory entry containing the
      contact information:

       CONTACT;ALTREP="ldap://example.com:6666/o=ABC%20Industries\,
        c=US???(cn=Jim%20Dolittle)":Jim Dolittle\, ABC Industries\,
        +1-919-555-1234

      The following is an example of this property with an alternate
      representation of a MIME body part containing the contact
      information, such as a vCard [RFC2426] embedded in a text/
      directory media type [RFC2425]:

       CONTACT;ALTREP="CID:part3.msg970930T083000SILVER@example.com":
        Jim Dolittle\, ABC Industries\, +1-919-555-1234



Desruisseaux                Standards Track                   [Page 110]

RFC 5545                       iCalendar                  September 2009


      The following is an example of this property referencing a network
      resource, such as a vCard [RFC2426] object containing the contact
      information:

       CONTACT;ALTREP="http://example.com/pdi/jdoe.vcf":Jim
         Dolittle\, ABC Industries\, +1-919-555-1234

3.8.4.3.  Organizer

   Property Name:  ORGANIZER

   Purpose:  This property defines the organizer for a calendar
      component.

   Value Type:  CAL-ADDRESS

   Property Parameters:  IANA, non-standard, language, common name,
      directory entry reference, and sent-by property parameters can be
      specified on this property.

   Conformance:  This property MUST be specified in an iCalendar object
      that specifies a group-scheduled calendar entity.  This property
      MUST be specified in an iCalendar object that specifies the
      publication of a calendar user's busy time.  This property MUST
      NOT be specified in an iCalendar object that specifies only a time
      zone definition or that defines calendar components that are not
      group-scheduled components, but are components only on a single
      user's calendar.

   Description:  This property is specified within the "VEVENT",
      "VTODO", and "VJOURNAL" calendar components to specify the
      organizer of a group-scheduled calendar entity.  The property is
      specified within the "VFREEBUSY" calendar component to specify the
      calendar user requesting the free or busy time.  When publishing a
      "VFREEBUSY" calendar component, the property is used to specify
      the calendar that the published busy time came from.

      The property has the property parameters "CN", for specifying the
      common or display name associated with the "Organizer", "DIR", for
      specifying a pointer to the directory information associated with
      the "Organizer", "SENT-BY", for specifying another calendar user
      that is acting on behalf of the "Organizer".  The non-standard
      parameters may also be specified on this property.  If the
      "LANGUAGE" property parameter is specified, the identified
      language applies to the "CN" parameter value.






Desruisseaux                Standards Track                   [Page 111]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This property is defined by the following
      notation:

       organizer  = "ORGANIZER" orgparam ":"
                    cal-address CRLF

       orgparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" cnparam) / (";" dirparam) / (";" sentbyparam) /
                  (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

   Example:  The following is an example of this property:

       ORGANIZER;CN=John Smith:mailto:jsmith@example.com

      The following is an example of this property with a pointer to the
      directory information associated with the organizer:

       ORGANIZER;CN=JohnSmith;DIR="ldap://example.com:6666/o=DC%20Ass
        ociates,c=US???(cn=John%20Smith)":mailto:jsmith@example.com

      The following is an example of this property used by another
      calendar user who is acting on behalf of the organizer, with
      responses intended to be sent back to the organizer, not the other
      calendar user:

       ORGANIZER;SENT-BY="mailto:jane_doe@example.com":
        mailto:jsmith@example.com

3.8.4.4.  Recurrence ID

   Property Name:  RECURRENCE-ID

   Purpose:  This property is used in conjunction with the "UID" and
      "SEQUENCE" properties to identify a specific instance of a
      recurring "VEVENT", "VTODO", or "VJOURNAL" calendar component.
      The property value is the original value of the "DTSTART" property
      of the recurrence instance.



Desruisseaux                Standards Track                   [Page 112]

RFC 5545                       iCalendar                  September 2009


   Value Type:  The default value type is DATE-TIME.  The value type can
      be set to a DATE value type.  This property MUST have the same
      value type as the "DTSTART" property contained within the
      recurring component.  Furthermore, this property MUST be specified
      as a date with local time if and only if the "DTSTART" property
      contained within the recurring component is specified as a date
      with local time.

   Property Parameters:  IANA, non-standard, value data type, time zone
      identifier, and recurrence identifier range parameters can be
      specified on this property.

   Conformance:  This property can be specified in an iCalendar object
      containing a recurring calendar component.

   Description:  The full range of calendar components specified by a
      recurrence set is referenced by referring to just the "UID"
      property value corresponding to the calendar component.  The
      "RECURRENCE-ID" property allows the reference to an individual
      instance within the recurrence set.

      If the value of the "DTSTART" property is a DATE type value, then
      the value MUST be the calendar date for the recurrence instance.

      The DATE-TIME value is set to the time when the original
      recurrence instance would occur; meaning that if the intent is to
      change a Friday meeting to Thursday, the DATE-TIME is still set to
      the original Friday meeting.

      The "RECURRENCE-ID" property is used in conjunction with the "UID"
      and "SEQUENCE" properties to identify a particular instance of a
      recurring event, to-do, or journal.  For a given pair of "UID" and
      "SEQUENCE" property values, the "RECURRENCE-ID" value for a
      recurrence instance is fixed.

      The "RANGE" parameter is used to specify the effective range of
      recurrence instances from the instance specified by the
      "RECURRENCE-ID" property value.  The value for the range parameter
      can only be "THISANDFUTURE" to indicate a range defined by the
      given recurrence instance and all subsequent instances.
      Subsequent instances are determined by their "RECURRENCE-ID" value
      and not their current scheduled start time.  Subsequent instances
      defined in separate components are not impacted by the given
      recurrence instance.  When the given recurrence instance is
      rescheduled, all subsequent instances are also rescheduled by the
      same time difference.  For instance, if the given recurrence
      instance is rescheduled to start 2 hours later, then all
      subsequent instances are also rescheduled 2 hours later.



Desruisseaux                Standards Track                   [Page 113]

RFC 5545                       iCalendar                  September 2009


      Similarly, if the duration of the given recurrence instance is
      modified, then all subsequence instances are also modified to have
      this same duration.

         Note: The "RANGE" parameter may not be appropriate to
         reschedule specific subsequent instances of complex recurring
         calendar component.  Assuming an unbounded recurring calendar
         component scheduled to occur on Mondays and Wednesdays, the
         "RANGE" parameter could not be used to reschedule only the
         future Monday instances to occur on Tuesday instead.  In such
         cases, the calendar application could simply truncate the
         unbounded recurring calendar component (i.e., with the "COUNT"
         or "UNTIL" rule parts), and create two new unbounded recurring
         calendar components for the future instances.

   Format Definition:  This property is defined by the following
      notation:

       recurid    = "RECURRENCE-ID" ridparam ":" ridval CRLF

       ridparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  (";" tzidparam) / (";" rangeparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       ridval     = date-time / date
       ;Value MUST match value type

   Example:  The following are examples of this property:

       RECURRENCE-ID;VALUE=DATE:19960401

       RECURRENCE-ID;RANGE=THISANDFUTURE:19960120T120000Z








Desruisseaux                Standards Track                   [Page 114]

RFC 5545                       iCalendar                  September 2009


3.8.4.5.  Related To

   Property Name:  RELATED-TO

   Purpose:  This property is used to represent a relationship or
      reference between one calendar component and another.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, and relationship type
      property parameters can be specified on this property.

   Conformance:  This property can be specified in the "VEVENT",
      "VTODO", and "VJOURNAL" calendar components.

   Description:  The property value consists of the persistent, globally
      unique identifier of another calendar component.  This value would
      be represented in a calendar component by the "UID" property.

      By default, the property value points to another calendar
      component that has a PARENT relationship to the referencing
      object.  The "RELTYPE" property parameter is used to either
      explicitly state the default PARENT relationship type to the
      referenced calendar component or to override the default PARENT
      relationship type and specify either a CHILD or SIBLING
      relationship.  The PARENT relationship indicates that the calendar
      component is a subordinate of the referenced calendar component.
      The CHILD relationship indicates that the calendar component is a
      superior of the referenced calendar component.  The SIBLING
      relationship indicates that the calendar component is a peer of
      the referenced calendar component.

      Changes to a calendar component referenced by this property can
      have an implicit impact on the related calendar component.  For
      example, if a group event changes its start or end date or time,
      then the related, dependent events will need to have their start
      and end dates changed in a corresponding way.  Similarly, if a
      PARENT calendar component is cancelled or deleted, then there is
      an implied impact to the related CHILD calendar components.  This
      property is intended only to provide information on the
      relationship of calendar components.  It is up to the target
      calendar system to maintain any property implications of this
      relationship.








Desruisseaux                Standards Track                   [Page 115]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This property is defined by the following
      notation:

       related    = "RELATED-TO" relparam ":" text CRLF

       relparam   = *(
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" reltypeparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

      The following is an example of this property:

       RELATED-TO:jsmith.part7.19960817T083000.xyzMail@example.com

       RELATED-TO:19960401-080045-4000F192713-0052@example.com

3.8.4.6.  Uniform Resource Locator

   Property Name:  URL

   Purpose:  This property defines a Uniform Resource Locator (URL)
      associated with the iCalendar object.

   Value Type:  URI

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified once in the "VEVENT",
      "VTODO", "VJOURNAL", or "VFREEBUSY" calendar components.

   Description:  This property may be used in a calendar component to
      convey a location where a more dynamic rendition of the calendar
      information associated with the calendar component can be found.
      This memo does not attempt to standardize the form of the URI, nor
      the format of the resource pointed to by the property value.  If
      the URL property and Content-Location MIME header are both
      specified, they MUST point to the same resource.




Desruisseaux                Standards Track                   [Page 116]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This property is defined by the following
      notation:

       url        = "URL" urlparam ":" uri CRLF

       urlparam   = *(";" other-param)

   Example:  The following is an example of this property:

       URL:http://example.com/pub/calendars/jsmith/mytime.ics

3.8.4.7.  Unique Identifier

   Property Name:  UID

   Purpose:  This property defines the persistent, globally unique
      identifier for the calendar component.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  The property MUST be specified in the "VEVENT",
      "VTODO", "VJOURNAL", or "VFREEBUSY" calendar components.

   Description:  The "UID" itself MUST be a globally unique identifier.
      The generator of the identifier MUST guarantee that the identifier
      is unique.  There are several algorithms that can be used to
      accomplish this.  A good method to assure uniqueness is to put the
      domain name or a domain literal IP address of the host on which
      the identifier was created on the right-hand side of an "@", and
      on the left-hand side, put a combination of the current calendar
      date and time of day (i.e., formatted in as a DATE-TIME value)
      along with some other currently unique (perhaps sequential)
      identifier available on the system (for example, a process id
      number).  Using a DATE-TIME value on the left-hand side and a
      domain name or domain literal on the right-hand side makes it
      possible to guarantee uniqueness since no two hosts should be
      using the same domain name or IP address at the same time.  Though
      other algorithms will work, it is RECOMMENDED that the right-hand
      side contain some domain identifier (either of the host itself or
      otherwise) such that the generator of the message identifier can
      guarantee the uniqueness of the left-hand side within the scope of
      that domain.

      This is the method for correlating scheduling messages with the
      referenced "VEVENT", "VTODO", or "VJOURNAL" calendar component.



Desruisseaux                Standards Track                   [Page 117]

RFC 5545                       iCalendar                  September 2009


      The full range of calendar components specified by a recurrence
      set is referenced by referring to just the "UID" property value
      corresponding to the calendar component.  The "RECURRENCE-ID"
      property allows the reference to an individual instance within the
      recurrence set.

      This property is an important method for group-scheduling
      applications to match requests with later replies, modifications,
      or deletion requests.  Calendaring and scheduling applications
      MUST generate this property in "VEVENT", "VTODO", and "VJOURNAL"
      calendar components to assure interoperability with other group-
      scheduling applications.  This identifier is created by the
      calendar system that generates an iCalendar object.

      Implementations MUST be able to receive and persist values of at
      least 255 octets for this property, but they MUST NOT truncate
      values in the middle of a UTF-8 multi-octet sequence.

   Format Definition:  This property is defined by the following
      notation:

       uid        = "UID" uidparam ":" text CRLF

       uidparam   = *(";" other-param)

   Example:  The following is an example of this property:

       UID:19960401T080045Z-4000F192713-0052@example.com

3.8.5.  Recurrence Component Properties

   The following properties specify recurrence information in calendar
   components.

3.8.5.1.  Exception Date-Times

   Property Name:  EXDATE

   Purpose:  This property defines the list of DATE-TIME exceptions for
      recurring events, to-dos, journal entries, or time zone
      definitions.

   Value Type:  The default value type for this property is DATE-TIME.
      The value type can be set to DATE.

   Property Parameters:  IANA, non-standard, value data type, and time
      zone identifier property parameters can be specified on this
      property.



Desruisseaux                Standards Track                   [Page 118]

RFC 5545                       iCalendar                  September 2009


   Conformance:  This property can be specified in recurring "VEVENT",
      "VTODO", and "VJOURNAL" calendar components as well as in the
      "STANDARD" and "DAYLIGHT" sub-components of the "VTIMEZONE"
      calendar component.

   Description:  The exception dates, if specified, are used in
      computing the recurrence set.  The recurrence set is the complete
      set of recurrence instances for a calendar component.  The
      recurrence set is generated by considering the initial "DTSTART"
      property along with the "RRULE", "RDATE", and "EXDATE" properties
      contained within the recurring component.  The "DTSTART" property
      defines the first instance in the recurrence set.  The "DTSTART"
      property value SHOULD match the pattern of the recurrence rule, if
      specified.  The recurrence set generated with a "DTSTART" property
      value that doesn't match the pattern of the rule is undefined.
      The final recurrence set is generated by gathering all of the
      start DATE-TIME values generated by any of the specified "RRULE"
      and "RDATE" properties, and then excluding any start DATE-TIME
      values specified by "EXDATE" properties.  This implies that start
      DATE-TIME values specified by "EXDATE" properties take precedence
      over those specified by inclusion properties (i.e., "RDATE" and
      "RRULE").  When duplicate instances are generated by the "RRULE"
      and "RDATE" properties, only one recurrence is considered.
      Duplicate instances are ignored.

      The "EXDATE" property can be used to exclude the value specified
      in "DTSTART".  However, in such cases, the original "DTSTART" date
      MUST still be maintained by the calendaring and scheduling system
      because the original "DTSTART" value has inherent usage
      dependencies by other properties such as the "RECURRENCE-ID".

   Format Definition:  This property is defined by the following
      notation:


















Desruisseaux                Standards Track                   [Page 119]

RFC 5545                       iCalendar                  September 2009


       exdate     = "EXDATE" exdtparam ":" exdtval *("," exdtval) CRLF

       exdtparam  = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                  ;
                  (";" tzidparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       exdtval    = date-time / date
       ;Value MUST match value type

   Example:  The following is an example of this property:

       EXDATE:19960402T010000Z,19960403T010000Z,19960404T010000Z

3.8.5.2.  Recurrence Date-Times

   Property Name:  RDATE

   Purpose:  This property defines the list of DATE-TIME values for
      recurring events, to-dos, journal entries, or time zone
      definitions.

   Value Type:  The default value type for this property is DATE-TIME.
      The value type can be set to DATE or PERIOD.

   Property Parameters:  IANA, non-standard, value data type, and time
      zone identifier property parameters can be specified on this
      property.

   Conformance:  This property can be specified in recurring "VEVENT",
      "VTODO", and "VJOURNAL" calendar components as well as in the
      "STANDARD" and "DAYLIGHT" sub-components of the "VTIMEZONE"
      calendar component.

   Description:  This property can appear along with the "RRULE"
      property to define an aggregate set of repeating occurrences.
      When they both appear in a recurring component, the recurrence



Desruisseaux                Standards Track                   [Page 120]

RFC 5545                       iCalendar                  September 2009


      instances are defined by the union of occurrences defined by both
      the "RDATE" and "RRULE".

      The recurrence dates, if specified, are used in computing the
      recurrence set.  The recurrence set is the complete set of
      recurrence instances for a calendar component.  The recurrence set
      is generated by considering the initial "DTSTART" property along
      with the "RRULE", "RDATE", and "EXDATE" properties contained
      within the recurring component.  The "DTSTART" property defines
      the first instance in the recurrence set.  The "DTSTART" property
      value SHOULD match the pattern of the recurrence rule, if
      specified.  The recurrence set generated with a "DTSTART" property
      value that doesn't match the pattern of the rule is undefined.
      The final recurrence set is generated by gathering all of the
      start DATE-TIME values generated by any of the specified "RRULE"
      and "RDATE" properties, and then excluding any start DATE-TIME
      values specified by "EXDATE" properties.  This implies that start
      DATE-TIME values specified by "EXDATE" properties take precedence
      over those specified by inclusion properties (i.e., "RDATE" and
      "RRULE").  Where duplicate instances are generated by the "RRULE"
      and "RDATE" properties, only one recurrence is considered.
      Duplicate instances are ignored.

   Format Definition:  This property is defined by the following
      notation:

       rdate      = "RDATE" rdtparam ":" rdtval *("," rdtval) CRLF

       rdtparam   = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" ("DATE-TIME" / "DATE" / "PERIOD")) /
                  (";" tzidparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       rdtval     = date-time / date / period
       ;Value MUST match value type






Desruisseaux                Standards Track                   [Page 121]

RFC 5545                       iCalendar                  September 2009


   Example:  The following are examples of this property:

       RDATE:19970714T123000Z
       RDATE;TZID=America/New_York:19970714T083000

       RDATE;VALUE=PERIOD:19960403T020000Z/19960403T040000Z,
        19960404T010000Z/PT3H

       RDATE;VALUE=DATE:19970101,19970120,19970217,19970421
        19970526,19970704,19970901,19971014,19971128,19971129,19971225

3.8.5.3.  Recurrence Rule

   Property Name:  RRULE

   Purpose:  This property defines a rule or repeating pattern for
      recurring events, to-dos, journal entries, or time zone
      definitions.

   Value Type:  RECUR

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in recurring "VEVENT",
      "VTODO", and "VJOURNAL" calendar components as well as in the
      "STANDARD" and "DAYLIGHT" sub-components of the "VTIMEZONE"
      calendar component, but it SHOULD NOT be specified more than once.
      The recurrence set generated with multiple "RRULE" properties is
      undefined.

   Description:  The recurrence rule, if specified, is used in computing
      the recurrence set.  The recurrence set is the complete set of
      recurrence instances for a calendar component.  The recurrence set
      is generated by considering the initial "DTSTART" property along
      with the "RRULE", "RDATE", and "EXDATE" properties contained
      within the recurring component.  The "DTSTART" property defines
      the first instance in the recurrence set.  The "DTSTART" property
      value SHOULD be synchronized with the recurrence rule, if
      specified.  The recurrence set generated with a "DTSTART" property
      value not synchronized with the recurrence rule is undefined.  The
      final recurrence set is generated by gathering all of the start
      DATE-TIME values generated by any of the specified "RRULE" and
      "RDATE" properties, and then excluding any start DATE-TIME values
      specified by "EXDATE" properties.  This implies that start DATE-
      TIME values specified by "EXDATE" properties take precedence over
      those specified by inclusion properties (i.e., "RDATE" and
      "RRULE").  Where duplicate instances are generated by the "RRULE"



Desruisseaux                Standards Track                   [Page 122]

RFC 5545                       iCalendar                  September 2009


      and "RDATE" properties, only one recurrence is considered.
      Duplicate instances are ignored.

      The "DTSTART" property specified within the iCalendar object
      defines the first instance of the recurrence.  In most cases, a
      "DTSTART" property of DATE-TIME value type used with a recurrence
      rule, should be specified as a date with local time and time zone
      reference to make sure all the recurrence instances start at the
      same local time regardless of time zone changes.

      If the duration of the recurring component is specified with the
      "DTEND" or "DUE" property, then the same exact duration will apply
      to all the members of the generated recurrence set.  Else, if the
      duration of the recurring component is specified with the
      "DURATION" property, then the same nominal duration will apply to
      all the members of the generated recurrence set and the exact
      duration of each recurrence instance will depend on its specific
      start time.  For example, recurrence instances of a nominal
      duration of one day will have an exact duration of more or less
      than 24 hours on a day where a time zone shift occurs.  The
      duration of a specific recurrence may be modified in an exception
      component or simply by using an "RDATE" property of PERIOD value
      type.

   Format Definition:  This property is defined by the following
      notation:

       rrule      = "RRULE" rrulparam ":" recur CRLF

       rrulparam  = *(";" other-param)

   Example:  All examples assume the Eastern United States time zone.

      Daily for 10 occurrences:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=DAILY;COUNT=10

       ==> (1997 9:00 AM EDT) September 2-11

      Daily until December 24, 1997:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=DAILY;UNTIL=19971224T000000Z

       ==> (1997 9:00 AM EDT) September 2-30;October 1-25
           (1997 9:00 AM EST) October 26-31;November 1-30;December 1-23




Desruisseaux                Standards Track                   [Page 123]

RFC 5545                       iCalendar                  September 2009


      Every other day - forever:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=DAILY;INTERVAL=2

       ==> (1997 9:00 AM EDT) September 2,4,6,8...24,26,28,30;
                              October 2,4,6...20,22,24
           (1997 9:00 AM EST) October 26,28,30;
                              November 1,3,5,7...25,27,29;
                              December 1,3,...

      Every 10 days, 5 occurrences:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=DAILY;INTERVAL=10;COUNT=5

       ==> (1997 9:00 AM EDT) September 2,12,22;
                              October 2,12

      Every day in January, for 3 years:

       DTSTART;TZID=America/New_York:19980101T090000

       RRULE:FREQ=YEARLY;UNTIL=20000131T140000Z;
        BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA
       or
       RRULE:FREQ=DAILY;UNTIL=20000131T140000Z;BYMONTH=1

       ==> (1998 9:00 AM EST)January 1-31
           (1999 9:00 AM EST)January 1-31
           (2000 9:00 AM EST)January 1-31

      Weekly for 10 occurrences:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=WEEKLY;COUNT=10

       ==> (1997 9:00 AM EDT) September 2,9,16,23,30;October 7,14,21
           (1997 9:00 AM EST) October 28;November 4












Desruisseaux                Standards Track                   [Page 124]

RFC 5545                       iCalendar                  September 2009


      Weekly until December 24, 1997:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=WEEKLY;UNTIL=19971224T000000Z

       ==> (1997 9:00 AM EDT) September 2,9,16,23,30;
                              October 7,14,21
           (1997 9:00 AM EST) October 28;
                              November 4,11,18,25;
                              December 2,9,16,23

      Every other week - forever:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=WEEKLY;INTERVAL=2;WKST=SU

       ==> (1997 9:00 AM EDT) September 2,16,30;
                              October 14
           (1997 9:00 AM EST) October 28;
                              November 11,25;
                              December 9,23
           (1998 9:00 AM EST) January 6,20;
                              February 3, 17
           ...

      Weekly on Tuesday and Thursday for five weeks:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=WEEKLY;UNTIL=19971007T000000Z;WKST=SU;BYDAY=TU,TH

       or

       RRULE:FREQ=WEEKLY;COUNT=10;WKST=SU;BYDAY=TU,TH

       ==> (1997 9:00 AM EDT) September 2,4,9,11,16,18,23,25,30;
                              October 2

      Every other week on Monday, Wednesday, and Friday until December
      24, 1997, starting on Monday, September 1, 1997:

       DTSTART;TZID=America/New_York:19970901T090000
       RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=19971224T000000Z;WKST=SU;
        BYDAY=MO,WE,FR

       ==> (1997 9:00 AM EDT) September 1,3,5,15,17,19,29;
                              October 1,3,13,15,17
           (1997 9:00 AM EST) October 27,29,31;
                              November 10,12,14,24,26,28;



Desruisseaux                Standards Track                   [Page 125]

RFC 5545                       iCalendar                  September 2009


                              December 8,10,12,22

      Every other week on Tuesday and Thursday, for 8 occurrences:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH

       ==> (1997 9:00 AM EDT) September 2,4,16,18,30;
                              October 2,14,16

      Monthly on the first Friday for 10 occurrences:

       DTSTART;TZID=America/New_York:19970905T090000
       RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR

       ==> (1997 9:00 AM EDT) September 5;October 3
           (1997 9:00 AM EST) November 7;December 5
           (1998 9:00 AM EST) January 2;February 6;March 6;April 3
           (1998 9:00 AM EDT) May 1;June 5

      Monthly on the first Friday until December 24, 1997:

       DTSTART;TZID=America/New_York:19970905T090000
       RRULE:FREQ=MONTHLY;UNTIL=19971224T000000Z;BYDAY=1FR

       ==> (1997 9:00 AM EDT) September 5; October 3
           (1997 9:00 AM EST) November 7; December 5

      Every other month on the first and last Sunday of the month for 10
      occurrences:

       DTSTART;TZID=America/New_York:19970907T090000
       RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;BYDAY=1SU,-1SU

       ==> (1997 9:00 AM EDT) September 7,28
           (1997 9:00 AM EST) November 2,30
           (1998 9:00 AM EST) January 4,25;March 1,29
           (1998 9:00 AM EDT) May 3,31

      Monthly on the second-to-last Monday of the month for 6 months:

       DTSTART;TZID=America/New_York:19970922T090000
       RRULE:FREQ=MONTHLY;COUNT=6;BYDAY=-2MO

       ==> (1997 9:00 AM EDT) September 22;October 20
           (1997 9:00 AM EST) November 17;December 22
           (1998 9:00 AM EST) January 19;February 16




Desruisseaux                Standards Track                   [Page 126]

RFC 5545                       iCalendar                  September 2009


      Monthly on the third-to-the-last day of the month, forever:

       DTSTART;TZID=America/New_York:19970928T090000
       RRULE:FREQ=MONTHLY;BYMONTHDAY=-3

       ==> (1997 9:00 AM EDT) September 28
           (1997 9:00 AM EST) October 29;November 28;December 29
           (1998 9:00 AM EST) January 29;February 26
           ...

      Monthly on the 2nd and 15th of the month for 10 occurrences:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=2,15

       ==> (1997 9:00 AM EDT) September 2,15;October 2,15
           (1997 9:00 AM EST) November 2,15;December 2,15
           (1998 9:00 AM EST) January 2,15

      Monthly on the first and last day of the month for 10 occurrences:

       DTSTART;TZID=America/New_York:19970930T090000
       RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=1,-1

       ==> (1997 9:00 AM EDT) September 30;October 1
           (1997 9:00 AM EST) October 31;November 1,30;December 1,31
           (1998 9:00 AM EST) January 1,31;February 1

      Every 18 months on the 10th thru 15th of the month for 10
      occurrences:

       DTSTART;TZID=America/New_York:19970910T090000
       RRULE:FREQ=MONTHLY;INTERVAL=18;COUNT=10;BYMONTHDAY=10,11,12,
        13,14,15

       ==> (1997 9:00 AM EDT) September 10,11,12,13,14,15
           (1999 9:00 AM EST) March 10,11,12,13

      Every Tuesday, every other month:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=MONTHLY;INTERVAL=2;BYDAY=TU

       ==> (1997 9:00 AM EDT) September 2,9,16,23,30
           (1997 9:00 AM EST) November 4,11,18,25
           (1998 9:00 AM EST) January 6,13,20,27;March 3,10,17,24,31
           ...




Desruisseaux                Standards Track                   [Page 127]

RFC 5545                       iCalendar                  September 2009


      Yearly in June and July for 10 occurrences:

       DTSTART;TZID=America/New_York:19970610T090000
       RRULE:FREQ=YEARLY;COUNT=10;BYMONTH=6,7

       ==> (1997 9:00 AM EDT) June 10;July 10
           (1998 9:00 AM EDT) June 10;July 10
           (1999 9:00 AM EDT) June 10;July 10
           (2000 9:00 AM EDT) June 10;July 10
           (2001 9:00 AM EDT) June 10;July 10

         Note: Since none of the BYDAY, BYMONTHDAY, or BYYEARDAY
         components are specified, the day is gotten from "DTSTART".

      Every other year on January, February, and March for 10
      occurrences:

       DTSTART;TZID=America/New_York:19970310T090000
       RRULE:FREQ=YEARLY;INTERVAL=2;COUNT=10;BYMONTH=1,2,3

       ==> (1997 9:00 AM EST) March 10
           (1999 9:00 AM EST) January 10;February 10;March 10
           (2001 9:00 AM EST) January 10;February 10;March 10
           (2003 9:00 AM EST) January 10;February 10;March 10

      Every third year on the 1st, 100th, and 200th day for 10
      occurrences:

       DTSTART;TZID=America/New_York:19970101T090000
       RRULE:FREQ=YEARLY;INTERVAL=3;COUNT=10;BYYEARDAY=1,100,200

       ==> (1997 9:00 AM EST) January 1
           (1997 9:00 AM EDT) April 10;July 19
           (2000 9:00 AM EST) January 1
           (2000 9:00 AM EDT) April 9;July 18
           (2003 9:00 AM EST) January 1
           (2003 9:00 AM EDT) April 10;July 19
           (2006 9:00 AM EST) January 1

      Every 20th Monday of the year, forever:

       DTSTART;TZID=America/New_York:19970519T090000
       RRULE:FREQ=YEARLY;BYDAY=20MO

       ==> (1997 9:00 AM EDT) May 19
           (1998 9:00 AM EDT) May 18
           (1999 9:00 AM EDT) May 17
           ...



Desruisseaux                Standards Track                   [Page 128]

RFC 5545                       iCalendar                  September 2009


      Monday of week number 20 (where the default start of the week is
      Monday), forever:

       DTSTART;TZID=America/New_York:19970512T090000
       RRULE:FREQ=YEARLY;BYWEEKNO=20;BYDAY=MO

       ==> (1997 9:00 AM EDT) May 12
           (1998 9:00 AM EDT) May 11
           (1999 9:00 AM EDT) May 17
           ...

      Every Thursday in March, forever:

       DTSTART;TZID=America/New_York:19970313T090000
       RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=TH

       ==> (1997 9:00 AM EST) March 13,20,27
           (1998 9:00 AM EST) March 5,12,19,26
           (1999 9:00 AM EST) March 4,11,18,25
           ...

      Every Thursday, but only during June, July, and August, forever:

       DTSTART;TZID=America/New_York:19970605T090000
       RRULE:FREQ=YEARLY;BYDAY=TH;BYMONTH=6,7,8

       ==> (1997 9:00 AM EDT) June 5,12,19,26;July 3,10,17,24,31;
                              August 7,14,21,28
           (1998 9:00 AM EDT) June 4,11,18,25;July 2,9,16,23,30;
                              August 6,13,20,27
           (1999 9:00 AM EDT) June 3,10,17,24;July 1,8,15,22,29;
                              August 5,12,19,26
           ...

      Every Friday the 13th, forever:

       DTSTART;TZID=America/New_York:19970902T090000
       EXDATE;TZID=America/New_York:19970902T090000
       RRULE:FREQ=MONTHLY;BYDAY=FR;BYMONTHDAY=13

       ==> (1998 9:00 AM EST) February 13;March 13;November 13
           (1999 9:00 AM EDT) August 13
           (2000 9:00 AM EDT) October 13
           ...







Desruisseaux                Standards Track                   [Page 129]

RFC 5545                       iCalendar                  September 2009


      The first Saturday that follows the first Sunday of the month,
      forever:

       DTSTART;TZID=America/New_York:19970913T090000
       RRULE:FREQ=MONTHLY;BYDAY=SA;BYMONTHDAY=7,8,9,10,11,12,13

       ==> (1997 9:00 AM EDT) September 13;October 11
           (1997 9:00 AM EST) November 8;December 13
           (1998 9:00 AM EST) January 10;February 7;March 7
           (1998 9:00 AM EDT) April 11;May 9;June 13...
           ...

      Every 4 years, the first Tuesday after a Monday in November,
      forever (U.S. Presidential Election day):

       DTSTART;TZID=America/New_York:19961105T090000
       RRULE:FREQ=YEARLY;INTERVAL=4;BYMONTH=11;BYDAY=TU;
        BYMONTHDAY=2,3,4,5,6,7,8

        ==> (1996 9:00 AM EST) November 5
            (2000 9:00 AM EST) November 7
            (2004 9:00 AM EST) November 2
            ...

      The third instance into the month of one of Tuesday, Wednesday, or
      Thursday, for the next 3 months:

       DTSTART;TZID=America/New_York:19970904T090000
       RRULE:FREQ=MONTHLY;COUNT=3;BYDAY=TU,WE,TH;BYSETPOS=3

       ==> (1997 9:00 AM EDT) September 4;October 7
           (1997 9:00 AM EST) November 6

      The second-to-last weekday of the month:

       DTSTART;TZID=America/New_York:19970929T090000
       RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-2

       ==> (1997 9:00 AM EDT) September 29
           (1997 9:00 AM EST) October 30;November 27;December 30
           (1998 9:00 AM EST) January 29;February 26;March 30
           ...









Desruisseaux                Standards Track                   [Page 130]

RFC 5545                       iCalendar                  September 2009


      Every 3 hours from 9:00 AM to 5:00 PM on a specific day:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=HOURLY;INTERVAL=3;UNTIL=19970902T170000Z

       ==> (September 2, 1997 EDT) 09:00,12:00,15:00

      Every 15 minutes for 6 occurrences:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=MINUTELY;INTERVAL=15;COUNT=6

       ==> (September 2, 1997 EDT) 09:00,09:15,09:30,09:45,10:00,10:15

      Every hour and a half for 4 occurrences:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=MINUTELY;INTERVAL=90;COUNT=4

       ==> (September 2, 1997 EDT) 09:00,10:30;12:00;13:30

      Every 20 minutes from 9:00 AM to 4:40 PM every day:

       DTSTART;TZID=America/New_York:19970902T090000
       RRULE:FREQ=DAILY;BYHOUR=9,10,11,12,13,14,15,16;BYMINUTE=0,20,40
       or
       RRULE:FREQ=MINUTELY;INTERVAL=20;BYHOUR=9,10,11,12,13,14,15,16

       ==> (September 2, 1997 EDT) 9:00,9:20,9:40,10:00,10:20,
                                   ... 16:00,16:20,16:40
           (September 3, 1997 EDT) 9:00,9:20,9:40,10:00,10:20,
                                   ...16:00,16:20,16:40
           ...

      An example where the days generated makes a difference because of
      WKST:

       DTSTART;TZID=America/New_York:19970805T090000
       RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=MO

       ==> (1997 EDT) August 5,10,19,24

      changing only WKST from MO to SU, yields different results...

       DTSTART;TZID=America/New_York:19970805T090000
       RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=SU

       ==> (1997 EDT) August 5,17,19,31



Desruisseaux                Standards Track                   [Page 131]

RFC 5545                       iCalendar                  September 2009


      An example where an invalid date (i.e., February 30) is ignored.

       DTSTART;TZID=America/New_York:20070115T090000
       RRULE:FREQ=MONTHLY;BYMONTHDAY=15,30;COUNT=5

       ==> (2007 EST) January 15,30
           (2007 EST) February 15
           (2007 EDT) March 15,30

3.8.6.  Alarm Component Properties

   The following properties specify alarm information in calendar
   components.

3.8.6.1.  Action

   Property Name:  ACTION

   Purpose:  This property defines the action to be invoked when an
      alarm is triggered.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be specified once in a "VALARM"
      calendar component.

   Description:  Each "VALARM" calendar component has a particular type
      of action with which it is associated.  This property specifies
      the type of action.  Applications MUST ignore alarms with x-name
      and iana-token values they don't recognize.

   Format Definition:  This property is defined by the following
      notation:

       action      = "ACTION" actionparam ":" actionvalue CRLF

       actionparam = *(";" other-param)


       actionvalue = "AUDIO" / "DISPLAY" / "EMAIL"
                   / iana-token / x-name

   Example:  The following are examples of this property in a "VALARM"
      calendar component:




Desruisseaux                Standards Track                   [Page 132]

RFC 5545                       iCalendar                  September 2009


       ACTION:AUDIO

       ACTION:DISPLAY

3.8.6.2.  Repeat Count

   Property Name:  REPEAT

   Purpose:  This property defines the number of times the alarm should
      be repeated, after the initial trigger.

   Value Type:  INTEGER

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in a "VALARM" calendar
      component.

   Description:  This property defines the number of times an alarm
      should be repeated after its initial trigger.  If the alarm
      triggers more than once, then this property MUST be specified
      along with the "DURATION" property.

   Format Definition:  This property is defined by the following
      notation:

       repeat  = "REPEAT" repparam ":" integer CRLF
       ;Default is "0", zero.

       repparam   = *(";" other-param)

   Example:  The following is an example of this property for an alarm
      that repeats 4 additional times with a 5-minute delay after the
      initial triggering of the alarm:

       REPEAT:4
       DURATION:PT5M

3.8.6.3.  Trigger

   Property Name:  TRIGGER

   Purpose:  This property specifies when an alarm will trigger.

   Value Type:  The default value type is DURATION.  The value type can
      be set to a DATE-TIME value type, in which case the value MUST
      specify a UTC-formatted DATE-TIME value.



Desruisseaux                Standards Track                   [Page 133]

RFC 5545                       iCalendar                  September 2009


   Property Parameters:  IANA, non-standard, value data type, time zone
      identifier, or trigger relationship property parameters can be
      specified on this property.  The trigger relationship property
      parameter MUST only be specified when the value type is
      "DURATION".

   Conformance:  This property MUST be specified in the "VALARM"
      calendar component.

   Description:  This property defines when an alarm will trigger.  The
      default value type is DURATION, specifying a relative time for the
      trigger of the alarm.  The default duration is relative to the
      start of an event or to-do with which the alarm is associated.
      The duration can be explicitly set to trigger from either the end
      or the start of the associated event or to-do with the "RELATED"
      parameter.  A value of START will set the alarm to trigger off the
      start of the associated event or to-do.  A value of END will set
      the alarm to trigger off the end of the associated event or to-do.

      Either a positive or negative duration may be specified for the
      "TRIGGER" property.  An alarm with a positive duration is
      triggered after the associated start or end of the event or to-do.
      An alarm with a negative duration is triggered before the
      associated start or end of the event or to-do.

      The "RELATED" property parameter is not valid if the value type of
      the property is set to DATE-TIME (i.e., for an absolute date and
      time alarm trigger).  If a value type of DATE-TIME is specified,
      then the property value MUST be specified in the UTC time format.
      If an absolute trigger is specified on an alarm for a recurring
      event or to-do, then the alarm will only trigger for the specified
      absolute DATE-TIME, along with any specified repeating instances.

      If the trigger is set relative to START, then the "DTSTART"
      property MUST be present in the associated "VEVENT" or "VTODO"
      calendar component.  If an alarm is specified for an event with
      the trigger set relative to the END, then the "DTEND" property or
      the "DTSTART" and "DURATION " properties MUST be present in the
      associated "VEVENT" calendar component.  If the alarm is specified
      for a to-do with a trigger set relative to the END, then either
      the "DUE" property or the "DTSTART" and "DURATION " properties
      MUST be present in the associated "VTODO" calendar component.

      Alarms specified in an event or to-do that is defined in terms of
      a DATE value type will be triggered relative to 00:00:00 of the
      user's configured time zone on the specified date, or relative to
      00:00:00 UTC on the specified date if no configured time zone can
      be found for the user.  For example, if "DTSTART" is a DATE value



Desruisseaux                Standards Track                   [Page 134]

RFC 5545                       iCalendar                  September 2009


      set to 19980205 then the duration trigger will be relative to
      19980205T000000 America/New_York for a user configured with the
      America/New_York time zone.

   Format Definition:  This property is defined by the following
      notation:

       trigger    = "TRIGGER" (trigrel / trigabs) CRLF

       trigrel    = *(
                  ;
                  ; The following are OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" "DURATION") /
                  (";" trigrelparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  ) ":"  dur-value

       trigabs    = *(
                  ;
                  ; The following is REQUIRED,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" "VALUE" "=" "DATE-TIME") /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  ) ":" date-time

   Example:  A trigger set 15 minutes prior to the start of the event or
      to-do.

       TRIGGER:-PT15M

      A trigger set five minutes after the end of an event or the due
      date of a to-do.

       TRIGGER;RELATED=END:PT5M




Desruisseaux                Standards Track                   [Page 135]

RFC 5545                       iCalendar                  September 2009


      A trigger set to an absolute DATE-TIME.

       TRIGGER;VALUE=DATE-TIME:19980101T050000Z

3.8.7.  Change Management Component Properties

   The following properties specify change management information in
   calendar components.

3.8.7.1.  Date-Time Created

   Property Name:  CREATED

   Purpose:  This property specifies the date and time that the calendar
      information was created by the calendar user agent in the calendar
      store.

         Note: This is analogous to the creation date and time for a
         file in the file system.

   Value Type:  DATE-TIME

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  The property can be specified once in "VEVENT",
      "VTODO", or "VJOURNAL" calendar components.  The value MUST be
      specified as a date with UTC time.

   Description:  This property specifies the date and time that the
      calendar information was created by the calendar user agent in the
      calendar store.

   Format Definition:  This property is defined by the following
      notation:

       created    = "CREATED" creaparam ":" date-time CRLF

       creaparam  = *(";" other-param)

   Example:  The following is an example of this property:

       CREATED:19960329T133000Z








Desruisseaux                Standards Track                   [Page 136]

RFC 5545                       iCalendar                  September 2009


3.8.7.2.  Date-Time Stamp

   Property Name:  DTSTAMP

   Purpose:  In the case of an iCalendar object that specifies a
      "METHOD" property, this property specifies the date and time that
      the instance of the iCalendar object was created.  In the case of
      an iCalendar object that doesn't specify a "METHOD" property, this
      property specifies the date and time that the information
      associated with the calendar component was last revised in the
      calendar store.

   Value Type:  DATE-TIME

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property MUST be included in the "VEVENT",
      "VTODO", "VJOURNAL", or "VFREEBUSY" calendar components.

   Description:  The value MUST be specified in the UTC time format.

      This property is also useful to protocols such as [2447bis] that
      have inherent latency issues with the delivery of content.  This
      property will assist in the proper sequencing of messages
      containing iCalendar objects.

      In the case of an iCalendar object that specifies a "METHOD"
      property, this property differs from the "CREATED" and "LAST-
      MODIFIED" properties.  These two properties are used to specify
      when the particular calendar data in the calendar store was
      created and last modified.  This is different than when the
      iCalendar object representation of the calendar service
      information was created or last modified.

      In the case of an iCalendar object that doesn't specify a "METHOD"
      property, this property is equivalent to the "LAST-MODIFIED"
      property.

   Format Definition:  This property is defined by the following
      notation:

       dtstamp    = "DTSTAMP" stmparam ":" date-time CRLF

       stmparam   = *(";" other-param)






Desruisseaux                Standards Track                   [Page 137]

RFC 5545                       iCalendar                  September 2009


   Example:

       DTSTAMP:19971210T080000Z

3.8.7.3.  Last Modified

   Property Name:  LAST-MODIFIED

   Purpose:  This property specifies the date and time that the
      information associated with the calendar component was last
      revised in the calendar store.

         Note: This is analogous to the modification date and time for a
         file in the file system.

   Value Type:  DATE-TIME

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified in the "VEVENT",
      "VTODO", "VJOURNAL", or "VTIMEZONE" calendar components.

   Description:  The property value MUST be specified in the UTC time
      format.

   Format Definition:  This property is defined by the following
      notation:

       last-mod   = "LAST-MODIFIED" lstparam ":" date-time CRLF

       lstparam   = *(";" other-param)

   Example:  The following is an example of this property:

       LAST-MODIFIED:19960817T133000Z

3.8.7.4.  Sequence Number

   Property Name:  SEQUENCE

   Purpose:  This property defines the revision sequence number of the
      calendar component within a sequence of revisions.

   Value Type:  INTEGER

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.



Desruisseaux                Standards Track                   [Page 138]

RFC 5545                       iCalendar                  September 2009


   Conformance:  The property can be specified in "VEVENT", "VTODO", or
      "VJOURNAL" calendar component.

   Description:  When a calendar component is created, its sequence
      number is 0.  It is monotonically incremented by the "Organizer's"
      CUA each time the "Organizer" makes a significant revision to the
      calendar component.

      The "Organizer" includes this property in an iCalendar object that
      it sends to an "Attendee" to specify the current version of the
      calendar component.

      The "Attendee" includes this property in an iCalendar object that
      it sends to the "Organizer" to specify the version of the calendar
      component to which the "Attendee" is referring.

      A change to the sequence number is not the mechanism that an
      "Organizer" uses to request a response from the "Attendees".  The
      "RSVP" parameter on the "ATTENDEE" property is used by the
      "Organizer" to indicate that a response from the "Attendees" is
      requested.

      Recurrence instances of a recurring component MAY have different
      sequence numbers.

   Format Definition:  This property is defined by the following
      notation:

       seq = "SEQUENCE" seqparam ":" integer CRLF
       ; Default is "0"

       seqparam   = *(";" other-param)

   Example:  The following is an example of this property for a calendar
      component that was just created by the "Organizer":

       SEQUENCE:0

      The following is an example of this property for a calendar
      component that has been revised two different times by the
      "Organizer":

       SEQUENCE:2

3.8.8.  Miscellaneous Component Properties

   The following properties specify information about a number of
   miscellaneous features of calendar components.



Desruisseaux                Standards Track                   [Page 139]

RFC 5545                       iCalendar                  September 2009


3.8.8.1.  IANA Properties

   Property Name:  An IANA-registered property name

   Value Type:  The default value type is TEXT.  The value type can be
      set to any value type.

   Property Parameters:  Any parameter can be specified on this
      property.

   Description:  This specification allows other properties registered
      with IANA to be specified in any calendar components.  Compliant
      applications are expected to be able to parse these other IANA-
      registered properties but can ignore them.

   Format Definition:  This property is defined by the following
      notation:

       iana-prop = iana-token *(";" icalparameter) ":" value CRLF

   Example:  The following are examples of properties that might be
      registered to IANA:

       DRESSCODE:CASUAL

       NON-SMOKING;VALUE=BOOLEAN:TRUE

3.8.8.2.  Non-Standard Properties

   Property Name:  Any property name with a "X-" prefix

   Purpose:  This class of property provides a framework for defining
      non-standard properties.

   Value Type:  The default value type is TEXT.  The value type can be
      set to any value type.

   Property Parameters:  IANA, non-standard, and language property
      parameters can be specified on this property.

   Conformance:  This property can be specified in any calendar
      component.

   Description:  The MIME Calendaring and Scheduling Content Type
      provides a "standard mechanism for doing non-standard things".
      This extension support is provided for implementers to "push the
      envelope" on the existing version of the memo.  Extension
      properties are specified by property and/or property parameter



Desruisseaux                Standards Track                   [Page 140]

RFC 5545                       iCalendar                  September 2009


      names that have the prefix text of "X-" (the two-character
      sequence: LATIN CAPITAL LETTER X character followed by the HYPHEN-
      MINUS character).  It is recommended that vendors concatenate onto
      this sentinel another short prefix text to identify the vendor.
      This will facilitate readability of the extensions and minimize
      possible collision of names between different vendors.  User
      agents that support this content type are expected to be able to
      parse the extension properties and property parameters but can
      ignore them.

      At present, there is no registration authority for names of
      extension properties and property parameters.  The value type for
      this property is TEXT.  Optionally, the value type can be any of
      the other valid value types.

   Format Definition:  This property is defined by the following
      notation:

       x-prop = x-name *(";" icalparameter) ":" value CRLF

   Example:  The following might be the ABC vendor's extension for an
      audio-clip form of subject property:

       X-ABC-MMSUBJ;VALUE=URI;FMTTYPE=audio/basic:http://www.example.
        org/mysubj.au

3.8.8.3.  Request Status

   Property Name:  REQUEST-STATUS

   Purpose:  This property defines the status code returned for a
      scheduling request.

   Value Type:  TEXT

   Property Parameters:  IANA, non-standard, and language property
      parameters can be specified on this property.

   Conformance:  The property can be specified in the "VEVENT", "VTODO",
      "VJOURNAL", or "VFREEBUSY" calendar component.

   Description:  This property is used to return status code information
      related to the processing of an associated iCalendar object.  The
      value type for this property is TEXT.







Desruisseaux                Standards Track                   [Page 141]

RFC 5545                       iCalendar                  September 2009


      The value consists of a short return status component, a longer
      return status description component, and optionally a status-
      specific data component.  The components of the value are
      separated by the SEMICOLON character.

      The short return status is a PERIOD character separated pair or
      3-tuple of integers.  For example, "3.1" or "3.1.1".  The
      successive levels of integers provide for a successive level of
      status code granularity.

      The following are initial classes for the return status code.
      Individual iCalendar object methods will define specific return
      status codes for these classes.  In addition, other classes for
      the return status code may be defined using the registration
      process defined later in this memo.

   +--------+----------------------------------------------------------+
   | Short  | Longer Return Status Description                         |
   | Return |                                                          |
   | Status |                                                          |
   | Code   |                                                          |
   +--------+----------------------------------------------------------+
   | 1.xx   | Preliminary success.  This class of status code          |
   |        | indicates that the request has been initially processed  |
   |        | but that completion is pending.                          |
   |        |                                                          |
   | 2.xx   | Successful.  This class of status code indicates that    |
   |        | the request was completed successfully.  However, the    |
   |        | exact status code can indicate that a fallback has been  |
   |        | taken.                                                   |
   |        |                                                          |
   | 3.xx   | Client Error.  This class of status code indicates that  |
   |        | the request was not successful.  The error is the result |
   |        | of either a syntax or a semantic error in the client-    |
   |        | formatted request.  Request should not be retried until  |
   |        | the condition in the request is corrected.               |
   |        |                                                          |
   | 4.xx   | Scheduling Error.  This class of status code indicates   |
   |        | that the request was not successful.  Some sort of error |
   |        | occurred within the calendaring and scheduling service,  |
   |        | not directly related to the request itself.              |
   +--------+----------------------------------------------------------+









Desruisseaux                Standards Track                   [Page 142]

RFC 5545                       iCalendar                  September 2009


   Format Definition:  This property is defined by the following
      notation:

       rstatus    = "REQUEST-STATUS" rstatparam ":"
                    statcode ";" statdesc [";" extdata]

       rstatparam = *(
                  ;
                  ; The following is OPTIONAL,
                  ; but MUST NOT occur more than once.
                  ;
                  (";" languageparam) /
                  ;
                  ; The following is OPTIONAL,
                  ; and MAY occur more than once.
                  ;
                  (";" other-param)
                  ;
                  )

       statcode   = 1*DIGIT 1*2("." 1*DIGIT)
       ;Hierarchical, numeric return status code

       statdesc   = text
       ;Textual status description

       extdata    = text
       ;Textual exception data.  For example, the offending property
       ;name and value or complete property line.

   Example:  The following are some possible examples of this property.

      The COMMA and SEMICOLON separator characters in the property value
      are BACKSLASH character escaped because they appear in a text
      value.

       REQUEST-STATUS:2.0;Success

       REQUEST-STATUS:3.1;Invalid property value;DTSTART:96-Apr-01

       REQUEST-STATUS:2.8; Success\, repeating event ignored. Scheduled
        as a single event.;RRULE:FREQ=WEEKLY\;INTERVAL=2

       REQUEST-STATUS:4.1;Event conflict.  Date-time is busy.

       REQUEST-STATUS:3.7;Invalid calendar user;ATTENDEE:
        mailto:jsmith@example.com




Desruisseaux                Standards Track                   [Page 143]

RFC 5545                       iCalendar                  September 2009


4.  iCalendar Object Examples

   The following examples are provided as an informational source of
   illustrative iCalendar objects consistent with this content type.

   The following example specifies a three-day conference that begins at
   2:30 P.M. UTC, September 18, 1996 and ends at 10:00 P.M. UTC,
   September 20, 1996.

       BEGIN:VCALENDAR
       PRODID:-//xyz Corp//NONSGML PDA Calendar Version 1.0//EN
       VERSION:2.0
       BEGIN:VEVENT
       DTSTAMP:19960704T120000Z
       UID:uid1@example.com
       ORGANIZER:mailto:jsmith@example.com
       DTSTART:19960918T143000Z
       DTEND:19960920T220000Z
       STATUS:CONFIRMED
       CATEGORIES:CONFERENCE
       SUMMARY:Networld+Interop Conference
       DESCRIPTION:Networld+Interop Conference
         and Exhibit\nAtlanta World Congress Center\n
        Atlanta\, Georgia
       END:VEVENT
       END:VCALENDAR

   The following example specifies a group-scheduled meeting that begins
   at 8:30 AM EST on March 12, 1998 and ends at 9:30 AM EST on March 12,
   1998.  The "Organizer" has scheduled the meeting with one or more
   calendar users in a group.  A time zone specification for Eastern
   United States has been specified.

       BEGIN:VCALENDAR
       PRODID:-//RDU Software//NONSGML HandCal//EN
       VERSION:2.0
       BEGIN:VTIMEZONE
       TZID:America/New_York
       BEGIN:STANDARD
       DTSTART:19981025T020000
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:19990404T020000
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400



Desruisseaux                Standards Track                   [Page 144]

RFC 5545                       iCalendar                  September 2009


       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE
       BEGIN:VEVENT
       DTSTAMP:19980309T231000Z
       UID:guid-1.example.com
       ORGANIZER:mailto:mrbig@example.com
       ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;CUTYPE=GROUP:
        mailto:employee-A@example.com
       DESCRIPTION:Project XYZ Review Meeting
       CATEGORIES:MEETING
       CLASS:PUBLIC
       CREATED:19980309T130000Z
       SUMMARY:XYZ Project Review
       DTSTART;TZID=America/New_York:19980312T083000
       DTEND;TZID=America/New_York:19980312T093000
       LOCATION:1CP Conference Room 4350
       END:VEVENT
       END:VCALENDAR

   The following is an example of an iCalendar object passed in a MIME
   message with a single body part consisting of a "text/calendar"
   Content Type.

       TO:jsmith@example.com
       FROM:jdoe@example.com
       MIME-VERSION:1.0
       MESSAGE-ID:<id3@example.com>
       CONTENT-TYPE:text/calendar; method="xyz"; component="VEVENT"

       BEGIN:VCALENDAR
       METHOD:xyz
       VERSION:2.0
       PRODID:-//ABC Corporation//NONSGML My Product//EN
       BEGIN:VEVENT
       DTSTAMP:19970324T120000Z
       SEQUENCE:0
       UID:uid3@example.com
       ORGANIZER:mailto:jdoe@example.com
       ATTENDEE;RSVP=TRUE:mailto:jsmith@example.com
       DTSTART:19970324T123000Z
       DTEND:19970324T210000Z
       CATEGORIES:MEETING,PROJECT
       CLASS:PUBLIC
       SUMMARY:Calendaring Interoperability Planning Meeting
       DESCRIPTION:Discuss how we can test c&s interoperability\n
        using iCalendar and other IETF standards.
       LOCATION:LDB Lobby



Desruisseaux                Standards Track                   [Page 145]

RFC 5545                       iCalendar                  September 2009


       ATTACH;FMTTYPE=application/postscript:ftp://example.com/pub/
        conf/bkgrnd.ps
       END:VEVENT
       END:VCALENDAR

   The following is an example of a to-do due on April 15, 1998.  An
   audio alarm has been specified to remind the calendar user at noon,
   the day before the to-do is expected to be completed and repeat
   hourly, four additional times.  The to-do definition has been
   modified twice since it was initially created.

       BEGIN:VCALENDAR
       VERSION:2.0
       PRODID:-//ABC Corporation//NONSGML My Product//EN
       BEGIN:VTODO
       DTSTAMP:19980130T134500Z
       SEQUENCE:2
       UID:uid4@example.com
       ORGANIZER:mailto:unclesam@example.com
       ATTENDEE;PARTSTAT=ACCEPTED:mailto:jqpublic@example.com
       DUE:19980415T000000
       STATUS:NEEDS-ACTION
       SUMMARY:Submit Income Taxes
       BEGIN:VALARM
       ACTION:AUDIO
       TRIGGER:19980403T120000Z
       ATTACH;FMTTYPE=audio/basic:http://example.com/pub/audio-
        files/ssbanner.aud
       REPEAT:4
       DURATION:PT1H
       END:VALARM
       END:VTODO
       END:VCALENDAR

   The following is an example of a journal entry:

       BEGIN:VCALENDAR
       VERSION:2.0
       PRODID:-//ABC Corporation//NONSGML My Product//EN
       BEGIN:VJOURNAL
       DTSTAMP:19970324T120000Z
       UID:uid5@example.com
       ORGANIZER:mailto:jsmith@example.com
       STATUS:DRAFT
       CLASS:PUBLIC
       CATEGORIES:Project Report,XYZ,Weekly Meeting
       DESCRIPTION:Project xyz Review Meeting Minutes\n
        Agenda\n1. Review of project version 1.0 requirements.\n2.



Desruisseaux                Standards Track                   [Page 146]

RFC 5545                       iCalendar                  September 2009


         Definition
        of project processes.\n3. Review of project schedule.\n
        Participants: John Smith\, Jane Doe\, Jim Dandy\n-It was
         decided that the requirements need to be signed off by
         product marketing.\n-Project processes were accepted.\n
        -Project schedule needs to account for scheduled holidays
         and employee vacation time. Check with HR for specific
         dates.\n-New schedule will be distributed by Friday.\n-
        Next weeks meeting is cancelled. No meeting until 3/23.
       END:VJOURNAL
       END:VCALENDAR

   The following is an example of published busy time information.  The
   iCalendar object might be placed in the network resource
   http://www.example.com/calendar/busytime/jsmith.ifb.

       BEGIN:VCALENDAR
       VERSION:2.0
       PRODID:-//RDU Software//NONSGML HandCal//EN
       BEGIN:VFREEBUSY
       ORGANIZER:mailto:jsmith@example.com
       DTSTART:19980313T141711Z
       DTEND:19980410T141711Z
       FREEBUSY:19980314T233000Z/19980315T003000Z
       FREEBUSY:19980316T153000Z/19980316T163000Z
       FREEBUSY:19980318T030000Z/19980318T040000Z
       URL:http://www.example.com/calendar/busytime/jsmith.ifb
       END:VFREEBUSY
       END:VCALENDAR

5.  Recommended Practices

   These recommended practices should be followed in order to assure
   consistent handling of the following cases for an iCalendar object.

   1.  Content lines longer than 75 octets SHOULD be folded.

   2.  When the combination of the "RRULE" and "RDATE" properties in a
       recurring component produces multiple instances having the same
       start DATE-TIME value, they should be collapsed to, and
       considered as, a single instance.  If the "RDATE" property is
       specified as a PERIOD value the duration of the recurrence
       instance will be the one specified by the "RDATE" property, and
       not the duration of the recurrence instance defined by the
       "DTSTART" property.

   3.  When a calendar user receives multiple requests for the same
       calendar component (e.g., REQUEST for a "VEVENT" calendar



Desruisseaux                Standards Track                   [Page 147]

RFC 5545                       iCalendar                  September 2009


       component) as a result of being on multiple mailing lists
       specified by "ATTENDEE" properties in the request, they SHOULD
       respond to only one of the requests.  The calendar user SHOULD
       also specify (using the "MEMBER" parameter of the "ATTENDEE"
       property) of which mailing list they are a member.

   4.  An implementation can truncate a "SUMMARY" property value to 255
       octets, but it MUST NOT truncate the value in the middle of a
       UTF-8 multi-octet sequence.

   5.  If seconds of the minute are not supported by an implementation,
       then a value of "00" SHOULD be specified for the seconds
       component in a time value.

   6.  "TZURL" values SHOULD NOT be specified as a file URI type.  This
       URI form can be useful within an organization, but is problematic
       in the Internet.

   7.  Some possible English values for "CATEGORIES" property include:
       "ANNIVERSARY", "APPOINTMENT", "BUSINESS", "EDUCATION", "HOLIDAY",
       "MEETING", "MISCELLANEOUS", "NON-WORKING HOURS", "NOT IN OFFICE",
       "PERSONAL", "PHONE CALL", "SICK DAY", "SPECIAL OCCASION",
       "TRAVEL", "VACATION".  Categories can be specified in any
       registered language.

   8.  Some possible English values for the "RESOURCES" property
       include: "CATERING", "CHAIRS", "COMPUTER PROJECTOR", "EASEL",
       "OVERHEAD PROJECTOR", "SPEAKER PHONE", "TABLE", "TV", "VCR",
       "VIDEO PHONE", "VEHICLE".  Resources can be specified in any
       registered language.

6.  Internationalization Considerations

   Applications MUST generate iCalendar streams in the UTF-8 charset and
   MUST accept an iCalendar stream in the UTF-8 or US-ASCII charset.

7.  Security Considerations

   Because calendaring and scheduling information is very privacy-
   sensitive, the protocol used for the transmission of calendaring and
   scheduling information should have capabilities to protect the
   information from possible threats, such as eavesdropping, replay,
   message insertion, deletion, modification, and man-in-the-middle
   attacks.

   As this document only defines the data format and media type of text/
   calendar that is independent of any calendar service or protocol, it
   is up to the actual protocol specifications such as iTIP [2446bis],



Desruisseaux                Standards Track                   [Page 148]

RFC 5545                       iCalendar                  September 2009


   iMIP [2447bis], and "Calendaring Extensions to WebDAV (CalDAV)"
   [RFC4791] to describe the threats that the above attacks present, as
   well as ways in which to mitigate them.

8.  IANA Considerations

8.1.  iCalendar Media Type Registration

   The Calendaring and Scheduling Core Object Specification is intended
   for use as a MIME content type.

   To: ietf-types@iana.org

   Subject: Registration of media type text/calendar

   Type name:  text

   Subtype name:  calendar

   Required parameters:  none

   Optional parameters:  charset, method, component, and optinfo

      The "charset" parameter is defined in [RFC2046] for subtypes of
      the "text" media type.  It is used to indicate the charset used in
      the body part.  The charset supported by this revision of
      iCalendar is UTF-8.  The use of any other charset is deprecated by
      this revision of iCalendar; however, note that this revision
      requires that compliant applications MUST accept iCalendar streams
      using either the UTF-8 or US-ASCII charset.

      The "method" parameter is used to convey the iCalendar object
      method or transaction semantics for the calendaring and scheduling
      information.  It also is an identifier for the restricted set of
      properties and values of which the iCalendar object consists.  The
      parameter is to be used as a guide for applications interpreting
      the information contained within the body part.  It SHOULD NOT be
      used to exclude or require particular pieces of information unless
      the identified method definition specifically calls for this
      behavior.  Unless specifically forbidden by a particular method
      definition, a text/calendar content type can contain any set of
      properties permitted by the Calendaring and Scheduling Core Object
      Specification.  The "method" parameter MUST be specified and MUST
      be set to the same value as the "METHOD" component property of the
      iCalendar objects of the iCalendar stream if and only if the
      iCalendar objects in the iCalendar stream all have a "METHOD"
      component property set to the same value.




Desruisseaux                Standards Track                   [Page 149]

RFC 5545                       iCalendar                  September 2009


      The value for the "method" parameter is defined as follows:

       method  = 1*(ALPHA / DIGIT / "-")
       ; IANA-registered iCalendar object method

      The "component" parameter conveys the type of iCalendar calendar
      component within the body part.  If the iCalendar object contains
      more than one calendar component type, then multiple component
      parameters MUST be specified.

      The value for the "component" parameter is defined as follows:

       component = "VEVENT"
                 / "VTODO"
                 / "VJOURNAL"
                 / "VFREEBUSY"
                 / "VTIMEZONE"
                 / iana-token
                 / x-name

      The "optinfo" parameter conveys optional information about the
      iCalendar object within the body part.  This parameter can only
      specify semantics already specified by the iCalendar object and
      that can be otherwise determined by parsing the body part.  In
      addition, the optional information specified by this parameter
      MUST be consistent with that information specified by the
      iCalendar object.  For example, it can be used to convey the
      "Attendee" response status to a meeting request.  The parameter
      value consists of a string value.

      The parameter can be specified multiple times.

      The value for the "optinfo" parameter is defined as follows:

       optinfo    = infovalue / qinfovalue

       infovalue  = iana-token / x-name

       qinfovalue = DQUOTE (infovalue) DQUOTE

   Encoding considerations:  This media type can contain 8bit
      characters, so the use of quoted-printable or base64 MIME Content-
      Transfer-Encodings might be necessary when iCalendar objects are
      transferred across protocols restricted to the 7bit repertoire.
      Note that a text valued property in the content entity can also
      have content encoding of special characters using a BACKSLASH
      character escapement technique.  This means that content values
      can end up being encoded twice.



Desruisseaux                Standards Track                   [Page 150]

RFC 5545                       iCalendar                  September 2009


   Security considerations:  See Section 7.

   Interoperability considerations:  This media type is intended to
      define a common format for conveying calendaring and scheduling
      information between different systems.  It is heavily based on the
      earlier [VCAL] industry specification.

   Published specification:  This specification.

   Applications that use this media type:  This media type is designed
      for widespread use by Internet calendaring and scheduling
      applications.  In addition, applications in the workflow and
      document management area might find this content-type applicable.
      The iTIP [2446bis], iMIP [2447bis], and CalDAV [RFC4791] Internet
      protocols directly use this media type also.

   Additional information:

      Magic number(s):  None.

      File extension(s):  The file extension of "ics" is to be used to
         designate a file containing (an arbitrary set of) calendaring
         and scheduling information consistent with this MIME content
         type.

         The file extension of "ifb" is to be used to designate a file
         containing free or busy time information consistent with this
         MIME content type.

      Macintosh file type code(s):  The file type code of "iCal" is to
         be used in Apple MacIntosh operating system environments to
         designate a file containing calendaring and scheduling
         information consistent with this MIME media type.

         The file type code of "iFBf" is to be used in Apple MacIntosh
         operating system environments to designate a file containing
         free or busy time information consistent with this MIME media
         type.

   Person & email address to contact for further information:  See the
      "Author's Address" section of this document.

   Intended usage:  COMMON

   Restrictions on usage:  There are no restrictions on where this media
      type can be used.

   Author:  See the "Author's Address" section of this document.



Desruisseaux                Standards Track                   [Page 151]

RFC 5545                       iCalendar                  September 2009


   Change controller:  IETF

8.2.  New iCalendar Elements Registration

   This section defines the process to register new or modified
   iCalendar elements, that is, components, properties, parameters,
   value data types, and values, with IANA.

8.2.1.  iCalendar Elements Registration Procedure

   The IETF will create a mailing list, icalendar@ietf.org, which can be
   used for public discussion of iCalendar elements proposals prior to
   registration.  Use of the mailing list is strongly encouraged.  The
   IESG will appoint a designated expert who will monitor the
   icalendar@ietf.org mailing list and review registrations.

   Registration of new iCalendar elements MUST be reviewed by the
   designated expert and published in an RFC.  A Standards Track RFC is
   REQUIRED for the registration of new value data types that modify
   existing properties, as well as for the registration of participation
   status values to be used in "VEVENT" calendar components.  A
   Standards Track RFC is also REQUIRED for registration of iCalendar
   elements that modify iCalendar elements previously documented in a
   Standards Track RFC.

   The registration procedure begins when a completed registration
   template, defined in the sections below, is sent to
   icalendar@ietf.org and iana@iana.org.  The designated expert is
   expected to tell IANA and the submitter of the registration within
   two weeks whether the registration is approved, approved with minor
   changes, or rejected with cause.  When a registration is rejected
   with cause, it can be re-submitted if the concerns listed in the
   cause are addressed.  Decisions made by the designated expert can be
   appealed to the IESG Applications Area Director, then to the IESG.
   They follow the normal appeals procedure for IESG decisions.

8.2.2.  Registration Template for Components

   A component is defined by completing the following template.

   Component name:  The name of the component.

   Purpose:  The purpose of the component.  Give a short but clear
      description.

   Format definition:  The ABNF for the component definition needs to be
      specified.




Desruisseaux                Standards Track                   [Page 152]

RFC 5545                       iCalendar                  September 2009


   Description:  Any special notes about the component, how it is to be
      used, etc.

   Example(s):  One or more examples of instances of the component need
      to be specified.

8.2.3.  Registration Template for Properties

   A property is defined by completing the following template.

   Property name:  The name of the property.

   Purpose:  The purpose of the property.  Give a short but clear
      description.

   Value type:  Any of the valid value types for the property value need
      to be specified.  The default value type also needs to be
      specified.

   Property parameters:  Any of the valid property parameters for the
      property MUST be specified.

   Conformance:  The calendar components in which the property can
      appear MUST be specified.

   Description:  Any special notes about the property, how it is to be
      used, etc.

   Format definition:  The ABNF for the property definition needs to be
      specified.

   Example(s):  One or more examples of instances of the property need
      to be specified.

8.2.4.  Registration Template for Parameters

   A parameter is defined by completing the following template.

   Parameter name:  The name of the parameter.

   Purpose:  The purpose of the parameter.  Give a short but clear
      description.

   Format definition:  The ABNF for the parameter definition needs to be
      specified.

   Description:  Any special notes about the parameter, how it is to be
      used, etc.



Desruisseaux                Standards Track                   [Page 153]

RFC 5545                       iCalendar                  September 2009


   Example(s):  One or more examples of instances of the parameter need
      to be specified.

8.2.5.  Registration Template for Value Data Types

   A value data type is defined by completing the following template.

   Value name:  The name of the value type.

   Purpose:  The purpose of the value type.  Give a short but clear
      description.

   Format definition:  The ABNF for the value type definition needs to
      be specified.

   Description:  Any special notes about the value type, how it is to be
      used, etc.

   Example(s):  One or more examples of instances of the value type need
      to be specified.

8.2.6.  Registration Template for Values

   A value is defined by completing the following template.

   Value:  The value literal.

   Purpose:  The purpose of the value.  Give a short but clear
      description.

   Conformance:  The calendar properties and/or parameters that can take
      this value need to be specified.

   Example(s):  One or more examples of instances of the value need to
      be specified.

   The following is a fictitious example of a registration of an
   iCalendar value:

   Value:  TOP-SECRET

   Purpose:  This value is used to specify the access classification of
      top-secret calendar components.

   Conformance:  This value can be used with the "CLASS" property.






Desruisseaux                Standards Track                   [Page 154]

RFC 5545                       iCalendar                  September 2009


   Example(s):  The following is an example of this value used with the
      "CLASS" property:

     CLASS:TOP-SECRET

8.3.  Initial iCalendar Elements Registries

   The IANA created and maintains the following registries for iCalendar
   elements with pointers to appropriate reference documents.

8.3.1.  Components Registry

   The following table has been used to initialize the components
   registry.

             +-----------+---------+-------------------------+
             | Component | Status  | Reference               |
             +-----------+---------+-------------------------+
             | VCALENDAR | Current | RFC 5545, Section 3.4   |
             |           |         |                         |
             | VEVENT    | Current | RFC 5545, Section 3.6.1 |
             |           |         |                         |
             | VTODO     | Current | RFC 5545, Section 3.6.2 |
             |           |         |                         |
             | VJOURNAL  | Current | RFC 5545, Section 3.6.3 |
             |           |         |                         |
             | VFREEBUSY | Current | RFC 5545, Section 3.6.4 |
             |           |         |                         |
             | VTIMEZONE | Current | RFC 5545, Section 3.6.5 |
             |           |         |                         |
             | VALARM    | Current | RFC 5545, Section 3.6.6 |
             |           |         |                         |
             | STANDARD  | Current | RFC 5545, Section 3.6.5 |
             |           |         |                         |
             | DAYLIGHT  | Current | RFC 5545, Section 3.6.5 |
             +-----------+---------+-------------------------+















Desruisseaux                Standards Track                   [Page 155]

RFC 5545                       iCalendar                  September 2009


8.3.2.  Properties Registry

   The following table is has been used to initialize the properties
   registry.

      +------------------+------------+----------------------------+
      | Property         | Status     | Reference                  |
      +------------------+------------+----------------------------+
      | CALSCALE         | Current    | RFC 5545, Section 3.7.1    |
      | METHOD           | Current    | RFC 5545, Section 3.7.2    |
      |                  |            |                            |
      | PRODID           | Current    | RFC 5545, Section 3.7.3    |
      |                  |            |                            |
      | VERSION          | Current    | RFC 5545, Section 3.7.4    |
      |                  |            |                            |
      | ATTACH           | Current    | RFC 5545, Section 3.8.1.1  |
      |                  |            |                            |
      | CATEGORIES       | Current    | RFC 5545, Section 3.8.1.2  |
      |                  |            |                            |
      | CLASS            | Current    | RFC 5545, Section 3.8.1.3  |
      |                  |            |                            |
      | COMMENT          | Current    | RFC 5545, Section 3.8.1.4  |
      |                  |            |                            |
      | DESCRIPTION      | Current    | RFC 5545, Section 3.8.1.5  |
      |                  |            |                            |
      | GEO              | Current    | RFC 5545, Section 3.8.1.6  |
      |                  |            |                            |
      | LOCATION         | Current    | RFC 5545, Section 3.8.1.7  |
      |                  |            |                            |
      | PERCENT-COMPLETE | Current    | RFC 5545, Section 3.8.1.8  |
      |                  |            |                            |
      | PRIORITY         | Current    | RFC 5545, Section 3.8.1.9  |
      |                  |            |                            |
      | RESOURCES        | Current    | RFC 5545, Section 3.8.1.10 |
      |                  |            |                            |
      | STATUS           | Current    | RFC 5545, Section 3.8.1.11 |
      |                  |            |                            |
      | SUMMARY          | Current    | RFC 5545, Section 3.8.1.12 |
      |                  |            |                            |
      | COMPLETED        | Current    | RFC 5545, Section 3.8.2.1  |
      |                  |            |                            |
      | DTEND            | Current    | RFC 5545, Section 3.8.2.2  |
      |                  |            |                            |
      | DUE              | Current    | RFC 5545, Section 3.8.2.3  |
      |                  |            |                            |
      | DTSTART          | Current    | RFC 5545, Section 3.8.2.4  |
      |                  |            |                            |
      | DURATION         | Current    | RFC 5545, Section 3.8.2.5  |



Desruisseaux                Standards Track                   [Page 156]

RFC 5545                       iCalendar                  September 2009


      |                  |            |                            |
      | FREEBUSY         | Current    | RFC 5545, Section 3.8.2.6  |
      |                  |            |                            |
      | TRANSP           | Current    | RFC 5545, Section 3.8.2.7  |
      |                  |            |                            |
      | TZID             | Current    | RFC 5545, Section 3.8.3.1  |
      |                  |            |                            |
      | TZNAME           | Current    | RFC 5545, Section 3.8.3.2  |
      |                  |            |                            |
      | TZOFFSETFROM     | Current    | RFC 5545, Section 3.8.3.3  |
      |                  |            |                            |
      | TZOFFSETTO       | Current    | RFC 5545, Section 3.8.3.4  |
      |                  |            |                            |
      | TZURL            | Current    | RFC 5545, Section 3.8.3.5  |
      |                  |            |                            |
      | ATTENDEE         | Current    | RFC 5545, Section 3.8.4.1  |
      |                  |            |                            |
      | CONTACT          | Current    | RFC 5545, Section 3.8.4.2  |
      |                  |            |                            |
      | ORGANIZER        | Current    | RFC 5545, Section 3.8.4.3  |
      |                  |            |                            |
      | RECURRENCE-ID    | Current    | RFC 5545, Section 3.8.4.4  |
      |                  |            |                            |
      | RELATED-TO       | Current    | RFC 5545, Section 3.8.4.5  |
      |                  |            |                            |
      | URL              | Current    | RFC 5545, Section 3.8.4.6  |
      |                  |            |                            |
      | UID              | Current    | RFC 5545, Section 3.8.4.7  |
      |                  |            |                            |
      | EXDATE           | Current    | RFC 5545, Section 3.8.5.1  |
      |                  |            |                            |
      | EXRULE           | Deprecated | [RFC2445], Section 4.8.5.2 |
      |                  |            |                            |
      | RDATE            | Current    | RFC 5545, Section 3.8.5.2  |
      |                  |            |                            |
      | RRULE            | Current    | RFC 5545, Section 3.8.5.3  |
      |                  |            |                            |
      | ACTION           | Current    | RFC 5545, Section 3.8.6.1  |
      |                  |            |                            |
      | REPEAT           | Current    | RFC 5545, Section 3.8.6.2  |
      |                  |            |                            |
      | TRIGGER          | Current    | RFC 5545, Section 3.8.6.3  |
      |                  |            |                            |
      | CREATED          | Current    | RFC 5545, Section 3.8.7.1  |
      |                  |            |                            |
      | DTSTAMP          | Current    | RFC 5545, Section 3.8.7.2  |
      |                  |            |                            |
      | LAST-MODIFIED    | Current    | RFC 5545, Section 3.8.7.3  |



Desruisseaux                Standards Track                   [Page 157]

RFC 5545                       iCalendar                  September 2009


      |                  |            |                            |
      | SEQUENCE         | Current    | RFC 5545, Section 3.8.7.4  |
      |                  |            |                            |
      | REQUEST-STATUS   | Current    | RFC 5545, Section 3.8.8.3  |
      +------------------+------------+----------------------------+

8.3.3.  Parameters Registry

   The following table has been used to initialize the parameters
   registry.

          +----------------+---------+--------------------------+
          | Parameter      | Status  | Reference                |
          +----------------+---------+--------------------------+
          | ALTREP         | Current | RFC 5545, Section 3.2.1  |
          |                |         |                          |
          | CN             | Current | RFC 5545, Section 3.2.2  |
          |                |         |                          |
          | CUTYPE         | Current | RFC 5545, Section 3.2.3  |
          |                |         |                          |
          | DELEGATED-FROM | Current | RFC 5545, Section 3.2.4  |
          |                |         |                          |
          | DELEGATED-TO   | Current | RFC 5545, Section 3.2.5  |
          |                |         |                          |
          | DIR            | Current | RFC 5545, Section 3.2.6  |
          |                |         |                          |
          | ENCODING       | Current | RFC 5545, Section 3.2.7  |
          |                |         |                          |
          | FMTTYPE        | Current | RFC 5545, Section 3.2.8  |
          |                |         |                          |
          | FBTYPE         | Current | RFC 5545, Section 3.2.9  |
          |                |         |                          |
          | LANGUAGE       | Current | RFC 5545, Section 3.2.10 |
          |                |         |                          |
          | MEMBER         | Current | RFC 5545, Section 3.2.11 |
          |                |         |                          |
          | PARTSTAT       | Current | RFC 5545, Section 3.2.12 |
          |                |         |                          |
          | RANGE          | Current | RFC 5545, Section 3.2.13 |
          |                |         |                          |
          | RELATED        | Current | RFC 5545, Section 3.2.14 |
          |                |         |                          |
          | RELTYPE        | Current | RFC 5545, Section 3.2.15 |
          |                |         |                          |
          | ROLE           | Current | RFC 5545, Section 3.2.16 |
          |                |         |                          |
          | RSVP           | Current | RFC 5545, Section 3.2.17 |
          |                |         |                          |



Desruisseaux                Standards Track                   [Page 158]

RFC 5545                       iCalendar                  September 2009


          | SENT-BY        | Current | RFC 5545, Section 3.2.18 |
          |                |         |                          |
          | TZID           | Current | RFC 5545, Section 3.2.19 |
          |                |         |                          |
          | VALUE          | Current | RFC 5545, Section 3.2.20 |
          +----------------+---------+--------------------------+

8.3.4.  Value Data Types Registry

   The following table has been used to initialize the value data types
   registry.

         +-----------------+---------+--------------------------+
         | Value Data Type | Status  | Reference                |
         +-----------------+---------+--------------------------+
         | BINARY          | Current | RFC 5545, Section 3.3.1  |
         |                 |         |                          |
         | BOOLEAN         | Current | RFC 5545, Section 3.3.2  |
         |                 |         |                          |
         | CAL-ADDRESS     | Current | RFC 5545, Section 3.3.3  |
         |                 |         |                          |
         | DATE            | Current | RFC 5545, Section 3.3.4  |
         |                 |         |                          |
         | DATE-TIME       | Current | RFC 5545, Section 3.3.5  |
         |                 |         |                          |
         | DURATION        | Current | RFC 5545, Section 3.3.6  |
         |                 |         |                          |
         | FLOAT           | Current | RFC 5545, Section 3.3.7  |
         |                 |         |                          |
         | INTEGER         | Current | RFC 5545, Section 3.3.8  |
         |                 |         |                          |
         | PERIOD          | Current | RFC 5545, Section 3.3.9  |
         |                 |         |                          |
         | RECUR           | Current | RFC 5545, Section 3.3.10 |
         |                 |         |                          |
         | TEXT            | Current | RFC 5545, Section 3.3.11 |
         |                 |         |                          |
         | TIME            | Current | RFC 5545, Section 3.3.12 |
         |                 |         |                          |
         | URI             | Current | RFC 5545, Section 3.3.13 |
         |                 |         |                          |
         | UTC-OFFSET      | Current | RFC 5545, Section 3.3.14 |
         +-----------------+---------+--------------------------+








Desruisseaux                Standards Track                   [Page 159]

RFC 5545                       iCalendar                  September 2009


8.3.5.  Calendar User Types Registry

   The following table has been used to initialize the calendar user
   types registry.

        +--------------------+---------+-------------------------+
        | Calendar User Type | Status  | Reference               |
        +--------------------+---------+-------------------------+
        | INDIVIDUAL         | Current | RFC 5545, Section 3.2.3 |
        |                    |         |                         |
        | GROUP              | Current | RFC 5545, Section 3.2.3 |
        |                    |         |                         |
        | RESOURCE           | Current | RFC 5545, Section 3.2.3 |
        |                    |         |                         |
        | ROOM               | Current | RFC 5545, Section 3.2.3 |
        |                    |         |                         |
        | UNKNOWN            | Current | RFC 5545, Section 3.2.3 |
        +--------------------+---------+-------------------------+

8.3.6.  Free/Busy Time Types Registry

   The following table has been used to initialize the free/busy time
   types registry.

        +---------------------+---------+-------------------------+
        | Free/Busy Time Type | Status  | Reference               |
        +---------------------+---------+-------------------------+
        | FREE                | Current | RFC 5545, Section 3.2.9 |
        |                     |         |                         |
        | BUSY                | Current | RFC 5545, Section 3.2.9 |
        |                     |         |                         |
        | BUSY-UNAVAILABLE    | Current | RFC 5545, Section 3.2.9 |
        |                     |         |                         |
        | BUSY-TENTATIVE      | Current | RFC 5545, Section 3.2.9 |
        +---------------------+---------+-------------------------+
















Desruisseaux                Standards Track                   [Page 160]

RFC 5545                       iCalendar                  September 2009


8.3.7.  Participation Statuses Registry

   The following table has been used to initialize the participation
   statuses registry.

        +--------------------+---------+--------------------------+
        | Participant Status | Status  | Reference                |
        +--------------------+---------+--------------------------+
        | NEEDS-ACTION       | Current | RFC 5545, Section 3.2.12 |
        |                    |         |                          |
        | ACCEPTED           | Current | RFC 5545, Section 3.2.12 |
        |                    |         |                          |
        | DECLINED           | Current | RFC 5545, Section 3.2.12 |
        |                    |         |                          |
        | TENTATIVE          | Current | RFC 5545, Section 3.2.12 |
        |                    |         |                          |
        | DELEGATED          | Current | RFC 5545, Section 3.2.12 |
        |                    |         |                          |
        | COMPLETED          | Current | RFC 5545, Section 3.2.12 |
        |                    |         |                          |
        | IN-PROCESS         | Current | RFC 5545, Section 3.2.12 |
        +--------------------+---------+--------------------------+

8.3.8.  Relationship Types Registry

   The following table has been used to initialize the relationship
   types registry.

        +-------------------+---------+--------------------------+
        | Relationship Type | Status  | Reference                |
        +-------------------+---------+--------------------------+
        | CHILD             | Current | RFC 5545, Section 3.2.15 |
        |                   |         |                          |
        | PARENT            | Current | RFC 5545, Section 3.2.15 |
        |                   |         |                          |
        | SIBLING           | Current | RFC 5545, Section 3.2.15 |
        +-------------------+---------+--------------------------+














Desruisseaux                Standards Track                   [Page 161]

RFC 5545                       iCalendar                  September 2009


8.3.9.  Participation Roles Registry

   The following table has been used to initialize the participation
   roles registry.

         +-----------------+---------+--------------------------+
         | Role Type       | Status  | Reference                |
         +-----------------+---------+--------------------------+
         | CHAIR           | Current | RFC 5545, Section 3.2.16 |
         |                 |         |                          |
         | REQ-PARTICIPANT | Current | RFC 5545, Section 3.2.16 |
         |                 |         |                          |
         | OPT-PARTICIPANT | Current | RFC 5545, Section 3.2.16 |
         |                 |         |                          |
         | NON-PARTICIPANT | Current | RFC 5545, Section 3.2.16 |
         +-----------------+---------+--------------------------+

8.3.10.  Actions Registry

   The following table has been used to initialize the actions registry.

          +-----------+------------+----------------------------+
          | Action    | Status     | Reference                  |
          +-----------+------------+----------------------------+
          | AUDIO     | Current    | RFC 5545, Section 3.8.6.1  |
          |           |            |                            |
          | DISPLAY   | Current    | RFC 5545, Section 3.8.6.1  |
          |           |            |                            |
          | EMAIL     | Current    | RFC 5545, Section 3.8.6.1  |
          |           |            |                            |
          | PROCEDURE | Deprecated | [RFC2445], Section 4.8.6.1 |
          +-----------+------------+----------------------------+

8.3.11.  Classifications Registry

   The following table has been used to initialize the classifications
   registry.

         +----------------+---------+---------------------------+
         | Classification | Status  | Reference                 |
         +----------------+---------+---------------------------+
         | PUBLIC         | Current | RFC 5545, Section 3.8.1.3 |
         |                |         |                           |
         | PRIVATE        | Current | RFC 5545, Section 3.8.1.3 |
         |                |         |                           |
         | CONFIDENTIAL   | Current | RFC 5545, Section 3.8.1.3 |
         +----------------+---------+---------------------------+




Desruisseaux                Standards Track                   [Page 162]

RFC 5545                       iCalendar                  September 2009


8.3.12.  Methods Registry

   No values are defined in this document for the "METHOD" property.

9.  Acknowledgments

   The editor of this document wishes to thank Frank Dawson and Derik
   Stenerson, the original authors of RFC 2445, as well as the following
   individuals who have participated in the drafting, review, and
   discussion of this memo:

   Joe Abley, Hervey Allen, Steve Allen, Jay Batson, Oliver Block,
   Stephane Bortzmeyer, Chris Bryant, Tantek Celik, Mark Crispin, Cyrus
   Daboo, Mike Douglass, Andrew N. Dowden, Lisa Dusseault, Lars Eggert,
   Gren Eliot, Pasi Eronen, Ben Fortuna, Ned Freed, Neal Gafter, Ted
   Hardie, Tim Hare, Jeffrey Harris, Helge Hess, Paul B. Hill, Thomas
   Hnetila, Russ Housley, Leif Johansson, Ciny Joy, Bruce Kahn, Reinhold
   Kainhofer, Martin Kiff, Patrice Lapierre, Michiel van Leeuwen,
   Jonathan Lennox, Jeff McCullough, Bill McQuillan, Alexey Melnikov,
   John W. Noerenberg II, Chuck Norris, Mark Paterson, Simon Pilette,
   Arnaud Quillaud, Robert Ransdell, Julian F. Reschke, Caleb
   Richardson, Sam Roberts, Dan Romascanu, Mike Samuel, George Sexton,
   Nigel Swinson, Clint Talbert, Simon Vaillancourt, Magnus Westerlund,
   and Sandy Wills.

   A special thanks to the working group chairs Aki Niemi and Eliot Lear
   for their support and guidance.

   The editor would also like to thank the Calendaring and Scheduling
   Consortium for advice with this specification, and for organizing
   interoperability testing events to help refine it.




















Desruisseaux                Standards Track                   [Page 163]

RFC 5545                       iCalendar                  September 2009


10.  References

10.1.  Normative References

   [ISO.8601.2004]        International Organization for
                          Standardization, "Data elements and
                          interchange formats -- Information interchange
                          -- Representation of dates and times", 2004.

   [ISO.9070.1991]        International Organization for
                          Standardization, "Information Technology_SGML
                          Support Facilities -- Registration Procedures
                          for Public Text Owner Identifiers, Second
                          Edition", April 1991.

   [RFC2045]              Freed, N. and N. Borenstein, "Multipurpose
                          Internet Mail Extensions (MIME) Part One:
                          Format of Internet Message Bodies", RFC 2045,
                          November 1996.

   [RFC2046]              Freed, N. and N. Borenstein, "Multipurpose
                          Internet Mail Extensions (MIME) Part Two:
                          Media Types", RFC 2046, November 1996.

   [RFC2119]              Bradner, S., "Key words for use in RFCs to
                          Indicate Requirement Levels", BCP 14,
                          RFC 2119, March 1997.

   [RFC2368]              Hoffman, P., Masinter, L., and J. Zawinski,
                          "The mailto URL scheme", RFC 2368, July 1998.

   [RFC3629]              Yergeau, F., "UTF-8, a transformation format
                          of ISO 10646", STD 63, RFC 3629,
                          November 2003.

   [RFC3986]              Berners-Lee, T., Fielding, R., and L.
                          Masinter, "Uniform Resource Identifier (URI):
                          Generic Syntax", STD 66, RFC 3986,
                          January 2005.

   [RFC4288]              Freed, N. and J. Klensin, "Media Type
                          Specifications and Registration Procedures",
                          BCP 13, RFC 4288, December 2005.

   [RFC4648]              Josefsson, S., "The Base16, Base32, and Base64
                          Data Encodings", RFC 4648, October 2006.





Desruisseaux                Standards Track                   [Page 164]

RFC 5545                       iCalendar                  September 2009


   [RFC5234]              Crocker, D. and P. Overell, "Augmented BNF for
                          Syntax Specifications: ABNF", STD 68,
                          RFC 5234, January 2008.

   [RFC5646]              Phillips, A., Ed., and M. Davis, Ed., "Tags
                          for Identifying Languages", BCP 47, RFC 5646,
                          September 2009.

   [US-ASCII]             American National Standards Institute, "Coded
                          Character Set - 7-bit American Standard Code
                          for Information Interchange", ANSI X3.4, 1986.

10.2.  Informative References

   [2446bis]              Daboo, C., "iCalendar Transport-Independent
                          Interoperability Protocol (iTIP)", Work
                          in Progress, April 2009.

   [2447bis]              Melnikov, A., "iCalendar Message-Based
                          Interoperability Protocol (iMIP)", Work
                          in Progress, June 2008.

   [ANSI INCITS 61-1986]  International Committee for Information
                          Technology, "Representation of Geographic
                          Point Locations for Information Interchange
                          (formerly ANSI X3.61-1986 (R1997))", ANSI
                          INCITS 61-1986 (R2007), 2007.

   [RFC1738]              Berners-Lee, T., Masinter, L., and M.
                          McCahill, "Uniform Resource Locators (URL)",
                          RFC 1738, December 1994.

   [RFC2392]              Levinson, E., "Content-ID and Message-ID
                          Uniform Resource Locators", RFC 2392,
                          August 1998.

   [RFC2397]              Masinter, L., "The "data" URL scheme",
                          RFC 2397, August 1998.

   [RFC2425]              Howes, T., Smith, M., and F. Dawson, "A MIME
                          Content-Type for Directory Information",
                          RFC 2425, September 1998.

   [RFC2426]              Dawson, F. and T. Howes, "vCard MIME Directory
                          Profile", RFC 2426, September 1998.






Desruisseaux                Standards Track                   [Page 165]

RFC 5545                       iCalendar                  September 2009


   [RFC2445]              Dawson, F. and Stenerson, D., "Internet
                          Calendaring and Scheduling Core Object
                          Specification (iCalendar)", RFC 2445,
                          November 1998.

   [RFC2616]              Fielding, R., Gettys, J., Mogul, J., Frystyk,
                          H., Masinter, L., Leach, P., and T. Berners-
                          Lee, "Hypertext Transfer Protocol --
                          HTTP/1.1", RFC 2616, June 1999.

   [RFC2818]              Rescorla, E., "HTTP Over TLS", RFC 2818,
                          May 2000.

   [RFC4516]              Smith, M. and T. Howes, "Lightweight Directory
                          Access Protocol (LDAP): Uniform Resource
                          Locator", RFC 4516, June 2006.

   [RFC4791]              Daboo, C., Desruisseaux, B., and L. Dusseault,
                          "Calendaring Extensions to WebDAV (CalDAV)",
                          RFC 4791, March 2007.

   [TZDB]                 Eggert, P. and A.D. Olson, "Sources for Time
                          Zone and Daylight Saving Time Data",
                          July 2009,
                          <http://www.twinsun.com/tz/tz-link.htm>.

   [VCAL]                 Internet Mail Consortium, "vCalendar: The
                          Electronic Calendaring and Scheduling Exchange
                          Format", September 1996,
                          <http://www.imc.org/pdi/vcal-10.txt>.





















Desruisseaux                Standards Track                   [Page 166]

RFC 5545                       iCalendar                  September 2009


Appendix A.  Differences from RFC 2445

   This appendix contains a list of changes that have been made in the
   Internet Calendaring and Scheduling Core Object Specification from
   RFC 2445.

A.1.  New Restrictions

   1.  The "DTSTART" property SHOULD be synchronized with the recurrence
       rule, if specified.

   2.  The "RRULE" property SHOULD NOT occur more than once in a
       component.

   3.  The BYHOUR, BYMINUTE, and BYSECOND rule parts MUST NOT be
       specified in the "RRULE" property when the "DTSTART" property is
       specified as a DATE value.

   4.  The value type of the "DTEND" or "DUE" properties MUST match the
       value type of "DTSTART" property.

   5.  The "DURATION" property can no longer appear in "VFREEBUSY"
       components.

A.2.  Restrictions Removed

   1.  The "DTSTART" and "DTEND" properties are no longer required to be
       specified as date with local time and time zone reference when
       used with a recurrence rule.

A.3.  Deprecated Features

   1.  The "EXRULE" property can no longer be specified in a component.

   2.  The "THISANDPRIOR" value can no longer be used with the "RANGE"
       parameter.

   3.  The "PROCEDURE" value can no longer be used with the "ACTION"
       property.

   4.  The value type RECUR no longer allows multiple values to be
       specified by a COMMA-separated list of values.

   5.  x-name rule parts can no longer be specified in properties of
       RECUR value type (e.g., "RRULE"). x-param can be used on RECUR
       value type properties instead.





Desruisseaux                Standards Track                   [Page 167]

RFC 5545                       iCalendar                  September 2009


Author's Address

   Bernard Desruisseaux (editor)
   Oracle Corporation
   600 blvd. de Maisonneuve West
   Suite 1900
   Montreal, QC  H3A 3J2
   CANADA

   EMail: bernard.desruisseaux@oracle.com
   URI:   http://www.oracle.com/








































Desruisseaux                Standards Track                   [Page 168]