setInterval("setDate('2018-12-24 12:20:45')",);

 function setDate(setTime){

 var date = new Date();//获取系统当前时间

 var time = (date.getYear()+)+"-"+(date.getMonth()+)+"-"+date.getDate() +" "+date.getHours()+":"+date.getMinutes()+":"+date.getSeconds();

 var setDate = new Date(setTime);

 var leftTime = setDate.getTime()- date.getTime();

 /*

 var Day = parseInt(dg/86400000);

 var hg = dg - Day*86400000;

 var Hours = parseInt(hg/3600000);;

 var mg = hg - Hours*3600000;

 var Minutes = parseInt(mg/60000);

 var sg = mg - Minutes*60000;

 var s = parseInt(sg/1000);

 var dTime = Day + " 天 "+Hours + " 时 "+Minutes + " 分 "+s + " 秒 ";*/

 var d,h,m,s;

 if (leftTime>=) {

 d = Math.floor(leftTime////);

 h = Math.floor(leftTime///%);

 m = Math.floor(leftTime//%);

 s = Math.floor(leftTime/%);

 }

 var dTime = d + " 天 "+h + " 时 "+m + " 分 "+s + " 秒 ";

 //$("#time").html("倒计时:"+dTime);

 }