js jquery 计算两个时间差

一，把时间转化成相应格式，如2012/05/25

二，基本代码如下所示
            var dt1 = new Date(Date.parse(baokaoyear + "/1/1"));
              var dt2 = new Date(Date.parse(workstime));
              var dt3 = new Date(Date.parse(shistime));
              var dt4 = new Date(Date.parse(nianyue));
              var diff = parseInt((dt1.getTime() - dt2.getTime()) / (1000 * 60 * 60 * 24)); //工作天数
              var diffshi = parseInt((dt1.getTime() - dt3.getTime()) / (1000 * 60 * 60 * 24)); //实施天数
              var workdiff = parseInt((dt2.getTime() - dt4.getTime()) / (1000 * 60 * 60 * 24)); //出生到工作的时间差
              //判断信息真实性
              if(workdiff<=365*18){
                  alert("您工作的时候还未满18岁，系统怀疑您信息的真实性。");
                  return;
              }