- $values['value'] = gmdate(DATETIME_DATETIME_STORAGE_FORMAT, $start);
- $values['end_value'] = gmdate(DATETIME_DATETIME_STORAGE_FORMAT, $end);
+ $values['value'] = gmdate(DateTimeItemInterface::DATETIME_STORAGE_FORMAT, $start);
+ $values['end_value'] = gmdate(DateTimeItemInterface::DATETIME_STORAGE_FORMAT, $end);