Index: app/views/gantts/show.html.erb
===================================================================
--- app/views/gantts/show.html.erb	(revision 8296)
+++ app/views/gantts/show.html.erb	(working copy)
@@ -143,7 +143,7 @@
   width =  zoom - 1
   %>
   <div style="left:<%= left %>px;top:37px;width:<%= width %>px;height:<%= height %>px;font-size:0.7em;<%= "background:#f1f1f1;" if wday > 5 %>" class="gantt_hdr">
-  <%= day_name(wday).first %>
+  <%= abbr_day_name(wday).first %>
   </div>
   <%
   left = left + width + 1
Index: lib/redmine/i18n.rb
===================================================================
--- lib/redmine/i18n.rb	(revision 8296)
+++ lib/redmine/i18n.rb	(working copy)
@@ -52,7 +52,11 @@
     def day_name(day)
       ::I18n.t('date.day_names')[day % 7]
     end
-
+  
+    def abbr_day_name(day)
+      ::I18n.t('date.abbr_day_names')[day % 7]
+    end
+  
     def month_name(month)
       ::I18n.t('date.month_names')[month]
     end