diff --git a/fhem/CHANGED b/fhem/CHANGED
index 513feaa6d..d51f7f3c2 100644
--- a/fhem/CHANGED
+++ b/fhem/CHANGED
@@ -1,5 +1,6 @@
 # Add changes at the top of the list. Keep it in ASCII, and 80-char wide.
 # Do not insert empty lines here, update check depends on it.
+  - changed: 57_Calendar: avoid some warnings
   - bufix:   00_MQTT: fixed delete MQTT_DEVICE
   - update:  98_DOIFtools: suppress lookup windows in DOIF or DOIFtools
                 by attribute DOIFtoolsNoLookUp and DOIFtoolsNoLookUpInDOIF
diff --git a/fhem/FHEM/57_Calendar.pm b/fhem/FHEM/57_Calendar.pm
index 99f10627b..4b0c0fef7 100644
--- a/fhem/FHEM/57_Calendar.pm
+++ b/fhem/FHEM/57_Calendar.pm
@@ -2054,8 +2054,8 @@ sub Calendar_GetEvents($$$$) {
             if(defined($filterref)) {
                 next unless(&$filterref($event, $param));
             }
-            if(defined($t1)) { next if($event->end() < $t1); }
-            if(defined($t2)) { next if($event->start() > $t2); }
+            if(defined($t1)) { next if(defined($event->end()) && $event->end() < $t1); }
+            if(defined($t2)) { next if(defined($event->start()) && $event->start() > $t2); }
             push @result, $event;
         }
     }