transform immutable datetime to mutable when using the time helper

src/View/Helper/TimeHelper.php

@@ -333,6 +333,10 @@ class TimeHelper extends Helper
             return $invalid;
         }
 
+        if ($date instanceof \DateTimeImmutable) {
+            $date = $date->toMutable();
+        }
+
         try {
             $time = new Time($date);
             return $time->i18nFormat($format, $timezone);