在百度上回答的一个问题，修改之后 JS倒计时

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%
 String path = request.getContextPath();
 String basePath = request.getScheme() + "://"
   + request.getServerName() + ":" + request.getServerPort()
   + path + "/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
  <base href="<%=basePath%>">

  <title>倒计时 页面</title>
  <script type="text/javascript">
  
//document.write("");
function show_date_time() {
 //alert('') ;

 window.setTimeout("show_date_time()", 1000);
 BirthDay = new Date("9/06/2013 08:30:00");//这个日期是可以修改的
 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);
 document.getElementById("span_dt_dt").innerHTML = "<font color='green' align='center' size='8'>"
   + daysold
   + '天'
   + hrsold
   + '小时'
   + minsold
   + '分'
   + seconds
   + '秒'
   + "</font>";

 //<align=center> <font color="#0000ff">"+daysold+"天"+hrsold+"小时"+minsold+"分"+seconds+"秒"+"<br></font>
}

show_date_time();
</script>

 </head>

 <body onload="show_date_time();">
  <div>
   <font size="5" face="宋体" color="#0000ff">距离2013年高考开始还有:</font>
   <span id="span_dt_dt"></span>
  </div>

 </body>
</html>