diff --git a/modules/default/calendar/vendor/ical.js/node-ical.js b/modules/default/calendar/vendor/ical.js/node-ical.js
index 4da1fc4f..1d295f8c 100644
--- a/modules/default/calendar/vendor/ical.js/node-ical.js
+++ b/modules/default/calendar/vendor/ical.js/node-ical.js
@@ -43,8 +43,10 @@ ical.objectHandlers['END'] = function(val, params, curr, stack){
       }
     }
     for (var i in curr.exdates) {
-      rule += ' EXDATE:' + curr.exdates[i].toISOString().replace(/[-:]/g, '');
-      rule = rule.replace(/\.[0-9]{3}/, '');
+        if( typeof (curr.exdates[i]) === "date") {
+            rule += ' EXDATE:' + curr.exdates[i].toISOString().replace(/[-:]/g, '');
+            rule = rule.replace(/\.[0-9]{3}/, '');
+        }
     }
     try {
       curr.rrule = rrulestr(rule);