$(document).ready(function(){
   s1  =  "2018-1-1"  
           s2  =  "2018-10-1"
   alert(addDays(273))
           alert(dateDiff(s1,s2))  
});
function dateDiff(sDate1, sDate2){ //sDate1和sDate2是2002-12-18格式   
var aDate, oDate1, oDate2, iDays;   
aDate = sDate1.split("-") ;  
oDate1 = new Date(aDate[1] + '-' + aDate[2] + '-' + aDate[0]); //转换为12-18-2002格式   
aDate = sDate2.split("-");   
oDate2 = new Date(aDate[1] + '-' + aDate[2] + '-' + aDate[0]);   
iDays = parseInt(Math.abs(oDate1 - oDate2) / 1000 / 60 / 60 /24); //把相差的毫秒数转换为天数   
return iDays   
}
function addDays(addDays) {
var s = "2018-1-1"
var now=new Date(s.replace('-','/'));
var newdate=new Date();
var newtimems=now.getTime()+(addDays*24*60*60*1000);
newdate.setTime(newtimems);
return newdate.getMonth()+1+"-"+newdate.getDate();
}

2、时间加减分钟后得到的新时间

var mydate = new Date();
var year = mydate.getFullYear();
var month = mydate.getMonth() + 1;
var day = mydate.getDate();
var hour = mydate.getHours(); //获取当前小时数(0-23)
var minutes = mydate.getMinutes(); //获取当前分钟数(0-59) 
/**分鐘相減**/

function minusMinutes(date, value) {
     date.setMinutes(date.getMinutes() - value);
     return date;
}; 
function AddMinutes(date, value) {
     date.setMinutes(date.getMinutes() + value);
     return date;
}; 
var nowTime = year+"-"+month+"-"+day+" "+hour+":"+minutes;
var preTime =  minusMinutes(new Date(nowTime),150);