//excel日期转换函数
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 $myDateStr;
    } elseif(strpos($days,'.')!==0) {
        return str_replace('.','-',$days);
    }
    return $days;
}