Issue #3466510: Fix timezone bug

src/Plugin/CustomElementsFieldFormatter/TimestampCeFieldFormatter.php

@@ -71,7 +71,7 @@ class TimestampCeFieldFormatter extends RawCeFieldFormatter {
         $item->value,
         $this->configuration['date_format'],
         $this->configuration['custom_date_format'],
-        $this->configuration['timezone']
+        $this->configuration['timezone'] ?: NULL
       );
     }