diff --git a/src/pages/views/teamsbot/TeamsbotSessionView.tsx b/src/pages/views/teamsbot/TeamsbotSessionView.tsx
index 7d83652..e342d9b 100644
--- a/src/pages/views/teamsbot/TeamsbotSessionView.tsx
+++ b/src/pages/views/teamsbot/TeamsbotSessionView.tsx
@@ -187,7 +187,9 @@ export const TeamsbotSessionView: React.FC = () => {
 
   const _formatTime = (timestamp: string) => {
     try {
-      return new Date(timestamp).toLocaleTimeString('de-CH', { hour: '2-digit', minute: '2-digit', second: '2-digit' });
+      const dt = new Date(timestamp);
+      if (!timestamp || Number.isNaN(dt.getTime())) return '';
+      return dt.toLocaleTimeString('de-CH', { hour: '2-digit', minute: '2-digit', second: '2-digit' });
     } catch {
       return '';
     }