private function checktime(int $hour, int $minute, int $second)
    {
        if ($hour < 0 || $hour > 23) {
            return false;
        } elseif ($minute < 0 || $minute > 59) {
            return false;
        } elseif ($second < 0 || $second > 59) {
            return false;
        }

        return true;
    }