js倒计时小程序实现代码

<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！");
// -->

<form name="form1">   
<p align="center" align="center">   
<center>离2010年还有:<br>   
<input type="textarea" name="left" size="35" style="text-align: center">   
</center>   
</p>   
</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+&#39;年, &#39;+Monthleft+&#39;月, &#39;+Dateleft+&#39;天, &#39;+Hourleft+&#39;小时, &#39;+Minuteleft+&#39;分, &#39;+Secondleft+&#39;秒&#39; 
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>