diff --git a/timemanagement/templates/timemanagement/tm_ab_update.html b/timemanagement/templates/timemanagement/tm_ab_update.html
index a41c1c4..99d33d0 100644
--- a/timemanagement/templates/timemanagement/tm_ab_update.html
+++ b/timemanagement/templates/timemanagement/tm_ab_update.html
@@ -196,8 +196,10 @@
 		date_start = new Date(new_start[2], (parseInt(new_start[1])-1), new_start[0]);
 		date_end = new Date(new_end[2], (parseInt(new_end[1])-1), new_end[0]);
 		
-		$("#id_start").data("DateTimePicker").date(date_start);
-  		$("#id_end").data("DateTimePicker").date(date_end);
+		if(date_start != undefined && date_end != undefined){
+			$("#id_start").data("DateTimePicker").date(date_start);
+  			$("#id_end").data("DateTimePicker").date(date_end);
+		}
 		
 		if(+new_start == +new_end){
 		    sameday = true;