4 files changed, 22 insertions, 1 deletions
diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index d3af47bc6a..b0fadc4092 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Added Date#change (like Time#change) [DHH]
+
 * DateTime#to_time converts to Time unless out of range.  #8512 [Geoff Buesing]
 
 * Date#to_datetime, #to_s(:rfc822).  #8512 [Geoff Buesing]
diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index b104e5271a..c522256aea 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -38,6 +38,20 @@ module ActiveSupport #:nodoc:
             d = d + options.delete(:days) if options[:days]
             d
           end
+
+          # Returns a new Date where one or more of the elements have been changed according to the +options+ parameter.
+          #
+          # Examples:
+          #
+          #   Date.new(2007, 5, 12).change(:day => 1)                  # => Date.new(2007, 5, 12)
+          #   Date.new(2007, 5, 12).change(:year => 2005, :month => 1) # => Date.new(2005, 1, 12)
+          def change(options)
+            ::Date.new(
+              options[:year]  || self.year,
+              options[:month] || self.month,
+              options[:day]   || options[:mday] || self.day # mday is deprecated
+            )
+          end
         end
       end
     end
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index 1fdfbcdf45..8f9c2ffa70 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -61,7 +61,7 @@ module ActiveSupport #:nodoc:
             self.utc? ? :utc_time : :local_time,
             options[:year]  || self.year,
             options[:month] || self.month,
-            options[:mday]  || self.mday,
+            options[:day]   || options[:mday] || self.day, # mday is deprecated
             options[:hour]  || self.hour,
             options[:min]   || (options[:hour] ? 0 : self.min),
             options[:sec]   || ((options[:hour] || options[:min]) ? 0 : self.sec),
diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index 3557c11748..f9891c9358 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -21,4 +21,9 @@ class DateExtCalculationsTest < Test::Unit::TestCase
   def test_to_date
     assert_equal Date.new(2005, 2, 21), Date.new(2005, 2, 21).to_date
   end
+
+  def test_change
+    assert_equal Date.new(2005, 2, 21), Date.new(2005, 2, 11).change(:day => 21)
+    assert_equal Date.new(2007, 5, 11), Date.new(2005, 2, 11).change(:year => 2007, :month => 5)
+  end
 end