Index: sites/all/modules/calendar/includes/calendar.inc
===================================================================
--- sites/all/modules/calendar/includes/calendar.inc	(revision 51)
+++ sites/all/modules/calendar/includes/calendar.inc	(working copy)
@@ -83,7 +83,7 @@
   $weekdays = calendar_untranslated_days($items, $view);
   $today = date_format(date_now(date_default_timezone_name()), DATE_FORMAT_DATE);
   $month = date_format($curday, 'n');
-  $week = date_week($curday_date);
+  $week = intval(date_week($curday_date));
   $first_day = variable_get('date_first_day', 0);
 
   // move backwards to the first day of the week