Backports Date#>> from 1.9 so that calculations do the right thing around the calendar reform

Our next_month gives November for some late dates in September of 1582.
Related methods, last_*, and in general advance have the same issues.
This commit fixes those, see the test suite for expected behavior, which
we still run in 1.9 to ensure it matches as we do with other methods
defined in Date in 1.9.

1 files changed, 27 insertions, 0 deletions

diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index d5f3eed8c1..e70fc729ce 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -145,6 +145,10 @@ class DateExtCalculationsTest < Test::Unit::TestCase
     assert_equal Date.new(1999,2,28), Date.new(2000,2,29).last_year
   end
 
+  def test_last_year_in_calendar_reform
+    assert_equal Date.new(1582,10,4), Date.new(1583,10,14).last_year
+  end
+
   def test_next_year
     assert_equal Date.new(2006,6,5), Date.new(2005,6,5).next_year
   end
@@ -153,16 +157,28 @@ class DateExtCalculationsTest < Test::Unit::TestCase
     assert_equal Date.new(2001,2,28), Date.new(2000,2,29).next_year
   end
 
+  def test_next_year_in_calendar_reform
+    assert_equal Date.new(1582,10,4), Date.new(1581,10,10).next_year
+  end
+
   def test_yesterday
     assert_equal Date.new(2005,2,21), Date.new(2005,2,22).yesterday
     assert_equal Date.new(2005,2,28), Date.new(2005,3,2).yesterday.yesterday
   end
 
+  def test_yesterday_in_calendar_reform
+    assert_equal Date.new(1582,10,4), Date.new(1582,10,15).yesterday
+  end
+
   def test_tomorrow
     assert_equal Date.new(2005,2,23), Date.new(2005,2,22).tomorrow
     assert_equal Date.new(2005,3,2),  Date.new(2005,2,28).tomorrow.tomorrow
   end
 
+  def test_tomorrow_in_calendar_reform
+    assert_equal Date.new(1582,10,15), Date.new(1582,10,4).tomorrow
+  end
+
   def test_advance
     assert_equal Date.new(2006,2,28), Date.new(2005,2,28).advance(:years => 1)
     assert_equal Date.new(2005,6,28), Date.new(2005,2,28).advance(:months => 4)
@@ -174,6 +190,17 @@ class DateExtCalculationsTest < Test::Unit::TestCase
     assert_equal Date.new(2005,2,28), Date.new(2004,2,29).advance(:years => 1) #leap day plus one year
   end
 
+  def test_advance_calendar_reform
+    assert_equal Date.new(1582,10,15), Date.new(1582,10,4).advance(:days => 1)
+    assert_equal Date.new(1582,10,4), Date.new(1582,10,15).advance(:days => -1)
+    5.upto(14) do |day|
+      assert_equal Date.new(1582,10,4), Date.new(1582,9,day).advance(:months => 1)
+      assert_equal Date.new(1582,10,4), Date.new(1582,11,day).advance(:months => -1)
+      assert_equal Date.new(1582,10,4), Date.new(1581,10,day).advance(:years => 1)
+      assert_equal Date.new(1582,10,4), Date.new(1583,10,day).advance(:years => -1)
+    end
+  end
+
   def test_next_week
     assert_equal Date.new(2005,2,28), Date.new(2005,2,22).next_week
     assert_equal Date.new(2005,3,4), Date.new(2005,2,22).next_week(:friday)