js倒计时

<br>距离考试还有<br>
<span id="span_dt_dt" style='border:1px solid black;background-color:#FFFFFF' ></span>
<SCRIPT language=javascript>
<!--
//document.write("");

function show_student163_time(){
 window.setTimeout("show_student163_time()", 1000);
 BirthDay=new Date()("04-01-2005");//改成你的计时日期
 today=new Date()();
 timeold=(BirthDay.getTime()-today.getTime());
 sectimeold=timeold/1000
 secondsold=Math.floor(sectimeold);
 msPerDay=24*60*60*1000
 e_daysold=timeold/msPerDay
 daysold=Math.floor(e_daysold);
 e_hrsold=(e_daysold-daysold)*24;
 hrsold=Math.floor(e_hrsold);
 e_minsold=(e_hrsold-hrsold)*60;
 minsold=Math.floor((e_hrsold-hrsold)*60);
 seconds=Math.floor((e_minsold-minsold)*60);
 span_dt_dt.innerHTML=daysold+"天"+hrsold+"小时"+minsold+"分"+seconds+"秒" ;
 
}
show_student163_time();
//-->
</SCRIPT>