Index: openacs-4/packages/calendar/tcl/cal-item-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/calendar/tcl/cal-item-procs.tcl,v
diff -u -N -r1.35.2.6 -r1.35.2.7
--- openacs-4/packages/calendar/tcl/cal-item-procs.tcl	19 Feb 2021 09:47:12 -0000	1.35.2.6
+++ openacs-4/packages/calendar/tcl/cal-item-procs.tcl	25 Jan 2022 14:00:42 -0000	1.35.2.7
@@ -21,7 +21,20 @@
 } {
     A sanity check that the start time is before the end time.
 } {
-    return [db_string dates_valid_p_select {}]
+    try {
+        return [db_string dates_valid_p_select {
+            select CASE
+              WHEN cast(:start_date as timestamp with time zone)
+                   <=
+                   cast(:end_date as timestamp with time zone) THEN 1
+              ELSE 0
+            END from dual
+        }]
+    } on error {errmsg} {
+        # Invalid dates in input, definitely not ok.
+        ad_log warning $errmsg
+        return 0
+    }
 }
 
 ad_proc -public calendar::item::new {
Index: openacs-4/packages/calendar/tcl/cal-item-procs.xql
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/calendar/tcl/cal-item-procs.xql,v
diff -u -N -r1.11 -r1.11.2.1
--- openacs-4/packages/calendar/tcl/cal-item-procs.xql	30 Apr 2018 13:54:38 -0000	1.11
+++ openacs-4/packages/calendar/tcl/cal-item-procs.xql	25 Jan 2022 14:00:42 -0000	1.11.2.1
@@ -10,15 +10,6 @@
     </querytext>
 </fullquery>
 
-<fullquery name="calendar::item::dates_valid_p.dates_valid_p_select">      
-<querytext>          
-  select CASE
-    WHEN cast(:start_date as timestamp with time zone) <= cast(:end_date as timestamp with time zone) THEN 1
-    ELSE 0
-  END from dual
-</querytext>
-</fullquery>
-
 <fullquery name="calendar::item::get.select_item_data">      
 <querytext>
       select