eZ\Publish\Core\FieldType\DateAndTime\Type::fieldSettingsToHash PHP Method

    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;
    }