(js) Allow 2-letter short month names

Fixes #4766

UI/WebServerResources/js/Preferences/Preferences.service.js

@@ -158,7 +158,7 @@
         dateString = dateString.trim();
         // The default function of Angular Material doesn't handle non-latin characters.
         // This one does.
-        var re = /^((([a-zA-Z]|[^\x00-\x7F]){3,}|[0-9]{1,4})([ .,]+|[/-])){2}(([a-zA-Z]|[^\x00-\x7F]){3,}|[0-9]{1,4})$/;
+        var re = /^((([a-zA-Z]|[^\x00-\x7F]){2,}|[0-9]{1,4})([ .,]+|[/-])){2}(([a-zA-Z]|[^\x00-\x7F]){3,}|[0-9]{1,4})$/;
         return re.test(dateString);
       };
     }