/**
  * @param TransactionJournal $journal
  * @param string             $dateField
  *
  * @return string
  */
 public static function dateAsString(TransactionJournal $journal, string $dateField = '') : string
 {
     if ($dateField === '') {
         return $journal->date->format('Y-m-d');
     }
     if (!is_null($journal->{$dateField}) && $journal->{$dateField} instanceof Carbon) {
         // make field NULL
         $carbon = clone $journal->{$dateField};
         $journal->{$dateField} = null;
         $journal->save();
         // create meta entry
         $journal->setMeta($dateField, $carbon);
         // return that one instead.
         return $carbon->format('Y-m-d');
     }
     $metaField = $journal->getMeta($dateField);
     if (!is_null($metaField)) {
         $carbon = new Carbon($metaField);
         return $carbon->format('Y-m-d');
     }
     return '';
 }