<script type="text/javascript">
var year=2014;//năm
var month=5;//tháng
var day=15;//ngày
var h=12;//giờ
var i=0;//phút
var s=0;//giây
dateFuture1 = new Date(year,month,day,h,i,s);
function GetCount(ddate,iid){

dateNow = new Date(); //grab current date
amount = ddate.getTime() - dateNow.getTime(); //calc milliseconds between dates
delete dateNow;

// if time is already past
if(amount < 0){
document.getElementById(iid).innerHTML="Now!";
}
// else date is still good
else{
days=0;hours=0;mins=0;secs=0;out="";

amount = Math.floor(amount/1000);//kill the "milliseconds" so just secs

days=Math.floor(amount/86400);//days
amount=amount%86400;

hours=Math.floor(amount/3600);//hours
amount=amount%3600;

mins=Math.floor(amount/60);//minutes
amount=amount%60;

secs=Math.floor(amount);//seconds
out += (days<=9?'0':'')+days +" "+((days==1)?"Ngày":"Ngày")+", ";
out += (hours<=9?'0':'')+hours +" "+((hours==1)?"hour":"Giờ")+", ";
out += (mins<=9?'0':'')+mins +" "+((mins==1)?"min":"Phút")+", ";
out += (secs<=9?'0':'')+secs +" "+((secs==1)?"sec":"Giây")+", ";
out = out.substr(0,out.length-2);
document.getElementById(iid).innerHTML=out;

setTimeout(function(){GetCount(ddate,iid)}, 1000);
}
}

window.onload=function(){
GetCount(dateFuture1, 'countbox1');
//you can add additional countdowns here (just make sure you create dateFuture2 and countbox2 etc for each)
};
</script>
<div id="countbox1"></div>