Index:  lib/redmine/helpers/gantt.rb
===================================================================
--- lib/redmine/helpers/gantt.rb	(revision 11898)
+++ lib/redmine/helpers/gantt.rb	(working copy)
@@ -696,7 +696,7 @@
       end
 
       def self.sort_version_logic(version)
-        [(version.start_date || Date.new()), version.id]
+        [(version.effective_date || Date.new()), version.id]
       end
 
       def current_limit