Index: app/models/issue.rb
===================================================================
--- app/models/issue.rb	(revision 19891)
+++ app/models/issue.rb	(working copy)
@@ -49,7 +49,8 @@
 
   acts_as_event :title => Proc.new {|o| "#{o.tracker.name} ##{o.id} (#{o.status}): #{o.subject}"},
                 :url => Proc.new {|o| {:controller => 'issues', :action => 'show', :id => o.id}},
-                :type => Proc.new {|o| 'issue' + (o.closed? ? '-closed' : '') }
+                :type => Proc.new {|o| 'issue' + (o.closed? ? '-closed' : '') },
+                :datetime => Proc.new {|o| o.updated_on }
 
   acts_as_activity_provider :scope => preload(:project, :author, :tracker, :status),
                             :author_key => :author_id