Index: openacs-4/packages/calendar/www/cal-item-new.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/calendar/www/cal-item-new.tcl,v
diff -u -N -r1.41.2.6 -r1.41.2.7
--- openacs-4/packages/calendar/www/cal-item-new.tcl	25 Jan 2022 13:39:29 -0000	1.41.2.6
+++ openacs-4/packages/calendar/www/cal-item-new.tcl	25 Jan 2022 14:19:40 -0000	1.41.2.7
@@ -209,7 +209,10 @@
 
     set date [calendar::from_sql_datetime -sql_date $ansi_date  -format "YYY-MM-DD"]
     set repeat_p 0
-    if {[info exists start_time] && $start_time ne "" && $start_time != 0} {
+    if {[info exists start_time] &&
+        $start_time != 0 &&
+        [template::util::date::validate $start_time e]
+    } {
         # Set the start time
         set start_hour $start_time
         set start_time "{} {} {} $start_time 0 {} {HH24:MI}"