TimeWithZone: when crossing DST boundary, treat Durations of days, months or years as variable-length, and all other values as absolute length. A time + 24.hours will advance exactly 24 hours, but a time + 1.day will advance 23-25 hours, depending on the day. Ensure consistent behavior across all advancing methods.

3 files changed, 203 insertions, 12 deletions

diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index a540150329..f0c1a208a5 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *Edge*
 
+* TimeWithZone: when crossing DST boundary, treat Durations of days, months or years as variable-length, and all other values as absolute length. A time + 24.hours will advance exactly 24 hours, but a time + 1.day will advance 23-25 hours, depending on the day. Ensure consistent behavior across all advancing methods [Geoff Buesing]
+
 * Added TimeZone #=~, to support matching zones by regex in time_zone_select. #195 [Ernie Miller]
 
 * Added Array#second through Array#tenth as aliases for Array#[1] through Array#[9] [DHH]
diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
index bfc5b16039..7370a45931 100644
--- a/activesupport/lib/active_support/time_with_zone.rb
+++ b/activesupport/lib/active_support/time_with_zone.rb
@@ -159,19 +159,24 @@ module ActiveSupport
       utc == other
     end
     
-    # If wrapped +time+ is a DateTime, use DateTime#since instead of <tt>+</tt>.
-    # Otherwise, just pass on to +method_missing+.
     def +(other)
-      result = utc.acts_like?(:date) ? utc.since(other) : utc + other rescue utc.since(other)
-      result.in_time_zone(time_zone)
+      # If we're adding a Duration of variable length (i.e., years, months, days), move forward from #time,
+      # otherwise move forward from #utc, for accuracy when moving across DST boundaries
+      if duration_of_variable_length?(other)
+        method_missing(:+, other)
+      else
+        result = utc.acts_like?(:date) ? utc.since(other) : utc + other rescue utc.since(other)
+        result.in_time_zone(time_zone)
+      end
     end
-    
-    # If a time-like object is passed in, compare it with +utc+.
-    # Else if wrapped +time+ is a DateTime, use DateTime#ago instead of DateTime#-.
-    # Otherwise, just pass on to +method_missing+.
+
     def -(other)
+      # If we're subtracting a Duration of variable length (i.e., years, months, days), move backwards from #time,
+      # otherwise move backwards #utc, for accuracy when moving across DST boundaries
       if other.acts_like?(:time)
         utc - other
+      elsif duration_of_variable_length?(other)
+        method_missing(:-, other)
       else
         result = utc.acts_like?(:date) ? utc.ago(other) : utc - other rescue utc.ago(other)
         result.in_time_zone(time_zone)
@@ -179,15 +184,27 @@ module ActiveSupport
     end
     
     def since(other)
-      utc.since(other).in_time_zone(time_zone)
+      # If we're adding a Duration of variable length (i.e., years, months, days), move forward from #time,
+      # otherwise move forward from #utc, for accuracy when moving across DST boundaries
+      if duration_of_variable_length?(other)
+        method_missing(:since, other)
+      else
+        utc.since(other).in_time_zone(time_zone)
+      end
     end
     
     def ago(other)
-      utc.ago(other).in_time_zone(time_zone)
+      since(-other)
     end
-    
+
     def advance(options)
-      utc.advance(options).in_time_zone(time_zone)
+      # If we're advancing a value of variable length (i.e., years, months, days), advance from #time,
+      # otherwise advance from #utc, for accuracy when moving across DST boundaries
+      if options.detect {|k,v| [:years, :months, :days].include? k}
+        method_missing(:advance, options)
+      else
+        utc.advance(options).in_time_zone(time_zone)
+      end
     end
     
     %w(year mon month day mday hour min sec).each do |method_name|
@@ -279,5 +296,9 @@ module ActiveSupport
       def transfer_time_values_to_utc_constructor(time)
         ::Time.utc_time(time.year, time.month, time.day, time.hour, time.min, time.sec, time.respond_to?(:usec) ? time.usec : 0)
       end
+      
+      def duration_of_variable_length?(obj)
+        ActiveSupport::Duration === obj && obj.parts.flatten.detect {|p| [:years, :months, :days].include? p }
+      end
   end
 end
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index 0977cd8e50..ac52a1be0b 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -485,6 +485,7 @@ class TimeWithZoneTest < Test::Unit::TestCase
     twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2004,2,29))
     assert_equal "Mon, 28 Feb 2005 00:00:00 EST -05:00", twz.advance(:years => 1).inspect
     assert_equal "Mon, 28 Feb 2005 00:00:00 EST -05:00", twz.years_since(1).inspect
+    assert_equal "Mon, 28 Feb 2005 00:00:00 EST -05:00", twz.since(1.year).inspect
     assert_equal "Mon, 28 Feb 2005 00:00:00 EST -05:00", (twz + 1.year).inspect
   end
 
@@ -492,6 +493,7 @@ class TimeWithZoneTest < Test::Unit::TestCase
     twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2005,1,31))
     assert_equal "Mon, 28 Feb 2005 00:00:00 EST -05:00", twz.advance(:months => 1).inspect
     assert_equal "Mon, 28 Feb 2005 00:00:00 EST -05:00", twz.months_since(1).inspect
+    assert_equal "Mon, 28 Feb 2005 00:00:00 EST -05:00", twz.since(1.month).inspect
     assert_equal "Mon, 28 Feb 2005 00:00:00 EST -05:00", (twz + 1.month).inspect
   end
 
@@ -499,6 +501,7 @@ class TimeWithZoneTest < Test::Unit::TestCase
     twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2000,1,31))
     assert_equal "Tue, 29 Feb 2000 00:00:00 EST -05:00", twz.advance(:months => 1).inspect
     assert_equal "Tue, 29 Feb 2000 00:00:00 EST -05:00", twz.months_since(1).inspect
+    assert_equal "Tue, 29 Feb 2000 00:00:00 EST -05:00", twz.since(1.month).inspect
     assert_equal "Tue, 29 Feb 2000 00:00:00 EST -05:00", (twz + 1.month).inspect
   end
 
@@ -506,6 +509,7 @@ class TimeWithZoneTest < Test::Unit::TestCase
     twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,3,2,2))
     assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", twz.advance(:months => 1).inspect
     assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", twz.months_since(1).inspect
+    assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", twz.since(1.month).inspect
     assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", (twz + 1.month).inspect
   end
 
@@ -513,8 +517,172 @@ class TimeWithZoneTest < Test::Unit::TestCase
     twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,4,2,1,59,59))
     assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", twz.advance(:seconds => 1).inspect
     assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", (twz + 1).inspect
+    assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", twz.since(1).inspect
+    assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", twz.since(1.second).inspect
     assert_equal "Sun, 02 Apr 2006 03:00:00 EDT -04:00", (twz + 1.second).inspect
   end
+
+  def test_advance_1_day_across_spring_dst_transition
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,4,1,10,30))
+    # In 2006, spring DST transition occurred Apr 2 at 2AM; this day was only 23 hours long
+    # When we advance 1 day, we want to end up at the same time on the next day
+    assert_equal "Sun, 02 Apr 2006 10:30:00 EDT -04:00", twz.advance(:days => 1).inspect
+    assert_equal "Sun, 02 Apr 2006 10:30:00 EDT -04:00", twz.since(1.days).inspect
+    assert_equal "Sun, 02 Apr 2006 10:30:00 EDT -04:00", (twz + 1.days).inspect
+    assert_equal "Sun, 02 Apr 2006 10:30:01 EDT -04:00", twz.since(1.days + 1.second).inspect
+    assert_equal "Sun, 02 Apr 2006 10:30:01 EDT -04:00", (twz + 1.days + 1.second).inspect
+  end
+  
+  def test_advance_1_day_across_spring_dst_transition_backwards
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,4,2,10,30))
+    # In 2006, spring DST transition occurred Apr 2 at 2AM; this day was only 23 hours long
+    # When we advance back 1 day, we want to end up at the same time on the previous day
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.advance(:days => -1).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.ago(1.days).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", (twz - 1.days).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:01 EST -05:00", twz.ago(1.days - 1.second).inspect
+  end
+    
+  def test_advance_1_day_expressed_as_number_of_seconds_minutes_or_hours_across_spring_dst_transition
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,4,1,10,30))
+    # In 2006, spring DST transition occurred Apr 2 at 2AM; this day was only 23 hours long
+    # When we advance a specific number of hours, minutes or seconds, we want to advance exactly that amount
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", (twz + 86400).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", (twz + 86400.seconds).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", twz.since(86400).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", twz.since(86400.seconds).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", twz.advance(:seconds => 86400).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", (twz + 1440.minutes).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", twz.since(1440.minutes).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", twz.advance(:minutes => 1440).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", (twz + 24.hours).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", twz.since(24.hours).inspect
+    assert_equal "Sun, 02 Apr 2006 11:30:00 EDT -04:00", twz.advance(:hours => 24).inspect
+  end
+  
+  def test_advance_1_day_expressed_as_number_of_seconds_minutes_or_hours_across_spring_dst_transition_backwards
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,4,2,11,30))
+    # In 2006, spring DST transition occurred Apr 2 at 2AM; this day was only 23 hours long
+    # When we advance a specific number of hours, minutes or seconds, we want to advance exactly that amount
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", (twz - 86400).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", (twz - 86400.seconds).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.ago(86400).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.ago(86400.seconds).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.advance(:seconds => -86400).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", (twz - 1440.minutes).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.ago(1440.minutes).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.advance(:minutes => -1440).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", (twz - 24.hours).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.ago(24.hours).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.advance(:hours => -24).inspect
+  end
+  
+  def test_advance_1_day_across_fall_dst_transition
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,10,28,10,30))
+    # In 2006, fall DST transition occurred Oct 29 at 2AM; this day was 25 hours long
+    # When we advance 1 day, we want to end up at the same time on the next day
+    assert_equal "Sun, 29 Oct 2006 10:30:00 EST -05:00", twz.advance(:days => 1).inspect
+    assert_equal "Sun, 29 Oct 2006 10:30:00 EST -05:00", twz.since(1.days).inspect
+    assert_equal "Sun, 29 Oct 2006 10:30:00 EST -05:00", (twz + 1.days).inspect
+    assert_equal "Sun, 29 Oct 2006 10:30:01 EST -05:00", twz.since(1.days + 1.second).inspect
+    assert_equal "Sun, 29 Oct 2006 10:30:01 EST -05:00", (twz + 1.days + 1.second).inspect
+  end
+  
+  def test_advance_1_day_across_fall_dst_transition_backwards
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,10,29,10,30))
+    # In 2006, fall DST transition occurred Oct 29 at 2AM; this day was 25 hours long
+    # When we advance backwards 1 day, we want to end up at the same time on the previous day
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.advance(:days => -1).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.ago(1.days).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", (twz - 1.days).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:01 EDT -04:00", twz.ago(1.days - 1.second).inspect
+  end
+  
+  def test_advance_1_day_expressed_as_number_of_seconds_minutes_or_hours_across_fall_dst_transition
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,10,28,10,30))
+    # In 2006, fall DST transition occurred Oct 29 at 2AM; this day was 25 hours long
+    # When we advance a specific number of hours, minutes or seconds, we want to advance exactly that amount
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", (twz + 86400).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", (twz + 86400.seconds).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", twz.since(86400).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", twz.since(86400.seconds).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", twz.advance(:seconds => 86400).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", (twz + 1440.minutes).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", twz.since(1440.minutes).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", twz.advance(:minutes => 1440).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", (twz + 24.hours).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", twz.since(24.hours).inspect
+    assert_equal "Sun, 29 Oct 2006 09:30:00 EST -05:00", twz.advance(:hours => 24).inspect
+  end
+  
+  def test_advance_1_day_expressed_as_number_of_seconds_minutes_or_hours_across_fall_dst_transition_backwards
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,10,29,9,30))
+    # In 2006, fall DST transition occurred Oct 29 at 2AM; this day was 25 hours long
+    # When we advance a specific number of hours, minutes or seconds, we want to advance exactly that amount
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", (twz - 86400).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", (twz - 86400.seconds).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.ago(86400).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.ago(86400.seconds).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.advance(:seconds => -86400).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", (twz - 1440.minutes).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.ago(1440.minutes).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.advance(:minutes => -1440).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", (twz - 24.hours).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.ago(24.hours).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.advance(:hours => -24).inspect
+  end
+
+  def test_advance_1_month_across_spring_dst_transition
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,4,1,10,30))
+    assert_equal "Mon, 01 May 2006 10:30:00 EDT -04:00", twz.advance(:months => 1).inspect
+    assert_equal "Mon, 01 May 2006 10:30:00 EDT -04:00", twz.months_since(1).inspect
+    assert_equal "Mon, 01 May 2006 10:30:00 EDT -04:00", twz.since(1.month).inspect
+    assert_equal "Mon, 01 May 2006 10:30:00 EDT -04:00", (twz + 1.month).inspect
+  end
+
+  def test_advance_1_month_across_spring_dst_transition_backwards
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,5,1,10,30))
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.advance(:months => -1).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.months_ago(1).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", twz.ago(1.month).inspect
+    assert_equal "Sat, 01 Apr 2006 10:30:00 EST -05:00", (twz - 1.month).inspect
+  end
+
+  def test_advance_1_month_across_fall_dst_transition
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,10,28,10,30))
+    assert_equal "Tue, 28 Nov 2006 10:30:00 EST -05:00", twz.advance(:months => 1).inspect
+    assert_equal "Tue, 28 Nov 2006 10:30:00 EST -05:00", twz.months_since(1).inspect
+    assert_equal "Tue, 28 Nov 2006 10:30:00 EST -05:00", twz.since(1.month).inspect
+    assert_equal "Tue, 28 Nov 2006 10:30:00 EST -05:00", (twz + 1.month).inspect
+  end
+
+  def test_advance_1_month_across_fall_dst_transition_backwards
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,11,28,10,30))
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.advance(:months => -1).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.months_ago(1).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", twz.ago(1.month).inspect
+    assert_equal "Sat, 28 Oct 2006 10:30:00 EDT -04:00", (twz - 1.month).inspect
+  end
+  
+  def test_advance_1_year
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2008,2,15,10,30))
+    assert_equal "Sun, 15 Feb 2009 10:30:00 EST -05:00", twz.advance(:years => 1).inspect
+    assert_equal "Sun, 15 Feb 2009 10:30:00 EST -05:00", twz.years_since(1).inspect
+    assert_equal "Sun, 15 Feb 2009 10:30:00 EST -05:00", (twz + 1.year).inspect
+    assert_equal "Thu, 15 Feb 2007 10:30:00 EST -05:00", twz.advance(:years => -1).inspect
+    assert_equal "Thu, 15 Feb 2007 10:30:00 EST -05:00", twz.years_ago(1).inspect
+    assert_equal "Thu, 15 Feb 2007 10:30:00 EST -05:00", (twz - 1.year).inspect
+  end
+  
+  def test_advance_1_year_during_dst
+    twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2008,7,15,10,30))
+    assert_equal "Wed, 15 Jul 2009 10:30:00 EDT -04:00", twz.advance(:years => 1).inspect
+    assert_equal "Wed, 15 Jul 2009 10:30:00 EDT -04:00", twz.years_since(1).inspect
+    assert_equal "Wed, 15 Jul 2009 10:30:00 EDT -04:00", (twz + 1.year).inspect
+    assert_equal "Sun, 15 Jul 2007 10:30:00 EDT -04:00", twz.advance(:years => -1).inspect
+    assert_equal "Sun, 15 Jul 2007 10:30:00 EDT -04:00", twz.years_ago(1).inspect
+    assert_equal "Sun, 15 Jul 2007 10:30:00 EDT -04:00", (twz - 1.year).inspect
+  end
 end
 
 class TimeWithZoneMethodsForTimeAndDateTimeTest < Test::Unit::TestCase