<script>

window.onload = function(){

demo();

}

//函数

function demo(){

var endtime = new Date("2016,7,21,17:30:00"); //结束时间

var nowtime = new Date();

var time = parseInt((endtime.getTime() - nowtime.getTime())/1000);

var day  = parseInt(time/60/60/24);

var hour = parseInt(time/60/60%24);

var min  = parseInt(time/60%60);

var sec  = parseInt(time%60);

document.getElementById('show').innerHTML = bb(day)+' 天'+bb(hour)+" 小时"+bb(min)+' 分钟'+bb(sec)+' 秒';

setTimeout(demo,100);

}

//+0

function bb(i){

if (i<10) {

i = 0+i;

}else{

return i;

}

}

</script>