我们这里只要自己定义一下s与urodz的值就可以随意定义任何日期或节日的倒计时功能了，各位朋友可加以修改。
精确到天的倒计时
复制代码 代码如下:
<script language="JavaScript">
<!-- // (c) Henryk Gajewski
var urodz= new Date("09/19/2013");
var  s="中秋节";
var now = new Date();
var ile = urodz.getTime() - now.getTime();
var dni = Math.floor(ile / (1000 * 60 * 60 * 24));
if (dni > 1)
   document.write(""+s+"还有"+dni +"天")
else if (dni == 1)
     document.write("只有2天啦！")
else if (dni == 0)
     document.write("只有1天啦！")
else
    document.write("好象已经过了哦！");
// -->

精确到秒的javascript倒计时代码 
HTML代码: 
复制代码 代码如下:
<form name="form1">  
<div align="center" align="center">  
<center>离2010年还有:<br>  
<input type="textarea" name="left" size="35" style="text-align: center">  
</center>  
</div>  
</form>  
<script LANGUAGE="javascript">  
startclock()  
var timerID = null;  
var timerRunning = false;  
function showtime() {  
Today = new Date();  
var NowHour = Today.getHours();  
var NowMinute = Today.getMinutes();  
var NowMonth = Today.getMonth();  
var NowDate = Today.getDate();  
var NowYear = Today.getYear();  
var NowSecond = Today.getSeconds();  
if (NowYear <2000)  
NowYear=1900+NowYear;  
Today = null;  
Hourleft = 23 - NowHour  
Minuteleft = 59 - NowMinute  
Secondleft = 59 - NowSecond  
Yearleft = 2009 - NowYear  
Monthleft = 12 - NowMonth - 1
Dateleft = 31 - NowDate  
if (Secondleft<0)  
{  
Secondleft=60+Secondleft;  
Minuteleft=Minuteleft-1;  
}  
if (Minuteleft<0)  
{   
Minuteleft=60+Minuteleft;  
Hourleft=Hourleft-1;  
}  
if (Hourleft<0)  
{  
Hourleft=24+Hourleft;  
Dateleft=Dateleft-1;  
}  
if (Dateleft<0)  
{  
Dateleft=31+Dateleft;  
Monthleft=Monthleft-1;  
}  
if (Monthleft<0)  
{  
Monthleft=12+Monthleft;  
Yearleft=Yearleft-1;  
}  
Temp=Yearleft+'年, '+Monthleft+'月, '+Dateleft+'天, '+Hourleft+'小时, '+Minuteleft+'分, '+Secondleft+'秒'
document.form1.left.value=Temp;  
timerID = setTimeout("showtime()",1000);  
timerRunning = true;  
}  
var timerID = null;  
var timerRunning = false;  
function stopclock () {  
if(timerRunning)  
clearTimeout(timerID);  
timerRunning = false;  
}  
function startclock () {  
stopclock();  
showtime();  
}  
// -->  
</script>