Make distance_of_time_in_words work with DateTime offsets

Because DateTime#to_time returns self when it has a non-zero offset
and subtracting two DateTime instances returns a Rational then the
distance_of_time_in_words methods outputs an incorrect value.

This is fixed in master because we can rely on Ruby 1.9.3's
implementation of to_time but it can't be fixed on Ruby 1.8.7 as
there is no way to map the DateTime to a Time with a non-zero offset.

We can workaround the problem by casting to Float before doing
the subtraction in the distance_of_time_in_words method.

Closes #8390

2 files changed, 13 insertions, 2 deletions

diff --git a/actionpack/lib/action_view/helpers/date_helper.rb b/actionpack/lib/action_view/helpers/date_helper.rb
index e5a27389f1..99aa144d3a 100644
--- a/actionpack/lib/action_view/helpers/date_helper.rb
+++ b/actionpack/lib/action_view/helpers/date_helper.rb
@@ -71,8 +71,9 @@ module ActionView
 
         from_time = from_time.to_time if from_time.respond_to?(:to_time)
         to_time = to_time.to_time if to_time.respond_to?(:to_time)
-        distance_in_minutes = (((to_time - from_time).abs)/60.0).round
-        distance_in_seconds = ((to_time - from_time).abs).round
+        distance = (to_time.to_f - from_time.to_f).abs
+        distance_in_minutes = (distance / 60.0).round
+        distance_in_seconds = distance.round
 
         I18n.with_options :locale => options[:locale], :scope => options[:scope] do |locale|
           case distance_in_minutes
diff --git a/actionpack/test/template/date_helper_test.rb b/actionpack/test/template/date_helper_test.rb
index dd0aad7119..e4f84f8dd7 100644
--- a/actionpack/test/template/date_helper_test.rb
+++ b/actionpack/test/template/date_helper_test.rb
@@ -151,6 +151,16 @@ class DateHelperTest < ActionView::TestCase
     assert_equal "1 minute", distance_of_time_in_words(60.seconds, 0, true)
   end
 
+  def test_distance_in_words_with_offset_datetimes
+    start_date = DateTime.new 1975, 1, 31, 0, 0, 0, '+6'
+    end_date = DateTime.new 1977, 1, 31, 0, 0, 0, '+6'
+    assert_equal("about 2 years", distance_of_time_in_words(start_date, end_date))
+
+    start_date = DateTime.new 1982, 12, 3, 0, 0, 0, '+6'
+    end_date = DateTime.new 2010, 11, 30, 0, 0, 0, '+6'
+    assert_equal("almost 28 years", distance_of_time_in_words(start_date, end_date))
+  end
+
   def test_time_ago_in_words
     assert_equal "about 1 year", time_ago_in_words(1.year.ago - 1.day)
   end