Index: app/controllers/issues_controller.rb
===================================================================
--- app/controllers/issues_controller.rb	(revision 19958)
+++ app/controllers/issues_controller.rb	(working copy)
@@ -62,8 +62,17 @@
         end
         format.atom do
           @issues = @query.issues(:limit => Setting.feeds_limit.to_i)
+          @issues.each do |issue|
+            issue.method(:event_datetime)
+            issue.define_singleton_method(:event_datetime) do
+              issue.updated_on
+            end
+          end
           render_feed(@issues,
                       :title => "#{@project || Setting.app_title}: #{l(:label_issue_plural)}")
+          @issues.each do |issue|
+            issue.singleton_class.send(:remove_method, :event_datetime)
+          end
         end
         format.csv do
           @issues = @query.issues(:limit => Setting.issues_export_limit.to_i)