public function fieldSettingsToHash($fieldSettings) { $fieldSettingsHash = parent::fieldSettingsToHash($fieldSettings); if (isset($fieldSettingsHash['dateInterval'])) { $fieldSettingsHash['dateInterval'] = $fieldSettingsHash['dateInterval']->format('P%r%yY%r%mM%r%dDT%r%hH%iM%r%sS'); } return $fieldSettingsHash; }