JS显示时钟精确到毫秒

<script language="javascript">
function countdown(endtime, today)
{
	today = new Date();
	target_time=new Date(endtime);
	timeold=(target_time.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_minsold); 
	e_seconds=(e_minsold-minsold)*60;
	seconds=Math.floor(e_seconds); 
	e_millisecond=(e_seconds-seconds)*1000;
	millisecond=Math.floor(e_millisecond);
    millisecond10=Math.floor(millisecond/10);

	/*
	s = timeold: + timeold + <br>;
	s+= sectimeold: + sectimeold + <br>;
	s+= secondsold: + secondsold + <br>;
	s+= msPerDay: + msPerDay + <br>;
	s+= e_daysold: + e_daysold + <br>;
	s+= daysold: + daysold + <br>;
	s+= e_hrsold: + e_hrsold + <br>;
	s+= hrsold: + hrsold + <br>;
	s+= e_minsold: + e_minsold + <br>;
	s+= minsold: + minsold + <br>;
	s+= e_seconds: + e_seconds + <br>;
	s+= seconds: + seconds + <br>;
	s+= e_millisecond: + e_millisecond + <br>;
	s+= millisecond: + millisecond + <br>;
	s+= millisecond10: + millisecond10;
		document.write(s);
	*/

	the_element = document.getElementById(counttime);
	the_element.innerHTML="仅剩 "+daysold+"天"+hrsold+"小时"+minsold+"分"+seconds+"秒"+millisecond10/*+"毫秒"*/ ;
	
	//today.setSeconds(today.getSeconds() + 0.01);
	window.setTimeout("countdown(" + endtime + ", today)", 100); 
} 
</script>

<table>
  <tr>
    <td width="175">
    <SPAN id="counttime" style="FONT-WEIGHT: bold; COLOR: #000000; FONT-FAMILY:Arial"></SPAN> 
    <script language="javascript">
		var endtime = 1-1-2012 00:00:00;
		var today = new Date();
		countdown(endtime, today);
    </script>
   </td>
  </tr>
</table>