1 files changed, 21 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index cd412368dc..70a4768d13 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -5,6 +5,11 @@ module ActiveSupport #:nodoc:
       module Calculations
         def self.included(base) #:nodoc:
           base.extend(ClassMethods)
+          
+          base.send(:alias_method, :plus_without_duration, :+)
+          base.send(:alias_method, :+, :plus_with_duration)
+          base.send(:alias_method, :minus_without_duration, :-)
+          base.send(:alias_method, :-, :minus_with_duration)
         end
 
         module ClassMethods
@@ -190,6 +195,22 @@ module ActiveSupport #:nodoc:
         def tomorrow
           self.since(1.day)
         end
+        
+        def plus_with_duration(other) #:nodoc:
+          if ActiveSupport::Duration === other
+            other.since(self)
+          else
+            plus_without_duration(other)
+          end
+        end
+
+        def minus_with_duration(other) #:nodoc:
+          if ActiveSupport::Duration === other
+            other.until(self)
+          else
+            minus_without_duration(other)
+          end
+        end
       end
     end
   end