php 格利高里函数转化成时间戳

/**
 * 时间格式处理
 * @param $days
 * @param bool $time
 * @return string
 */
public function excelTime($days, $time=false){
    if(is_numeric($days)){
        //based on 1900-1-1
        $jd = gregoriantojd(1, 1, 1970);
        $gregorian = JDToGregorian($jd+intval($days)-25569);
        $myDate = explode('/',$gregorian);
        $myDateStr = str_pad($myDate[2],4,'0', STR_PAD_LEFT)
            ."-".str_pad($myDate[0],2,'0', STR_PAD_LEFT)
            ."-".str_pad($myDate[1],2,'0', STR_PAD_LEFT)
            .($time?" 00:00:00":'');
        return $myDateStr;
    }
    return $days;
}

注意：如果linux没有安装类库：
http://php.net/manual/zh/calendar.installation.php