public function toMySQLDate($withTime = true)
    {
        if ($this->isHollow()) {
            return $withTime ? '0000-00-00 00:00:00' : '0000-00-00';
        }

        $format = $withTime ? 'Y-m-d H:i:s' : 'Y-m-d';

        return $this->format($format);
    }