diff --git a/calendar/resources/content/pref/rootCalendarPref.js b/calendar/resources/content/pref/rootCalendarPref.js
index 4f6ff3a7d571..8b557e7082fa 100644
--- a/calendar/resources/content/pref/rootCalendarPref.js
+++ b/calendar/resources/content/pref/rootCalendarPref.js
@@ -60,7 +60,7 @@ calendarPrefObserver.prototype =
 
          case "calendar.date.format" :
             this.CalendarPreferences.calendarWindow.currentView.refresh();
-            unifinderRefresh();
+            refreshEventTree( getAndSetEventTable() );
             toDoUnifinderRefresh();
          default :
             break;