This JavaScript displays the days, hours, minutes and seconds left to the given date:

   1  function Countdown(then) {
   2  
   3  	this.then = then;
   4  	
   5  	function setElement(id, value) {
   6  		if (value.length < 2) {
   7  	    	value = "0" + value;
   8  		}
   9  	
  10  		window.document.getElementById(id).innerHTML = value;
  11  	}
  12  	
  13  	function countdown() {
  14  		now  		  = new Date();
  15  	  	diff		  = new Date(this.then - now);
  16  	  	
  17  		seconds_left  = Math.floor(diff.valueOf() / 1000);
  18  	
  19  		seconds  = Math.floor(seconds_left / 1) % 60;
  20  		minutes  = Math.floor(seconds_left / 60) % 60;
  21  		hours    = Math.floor(seconds_left / 3600) % 24;
  22  		days     = Math.floor(seconds_left / 86400) % 86400;
  23  		
  24  		setElement('countdown-days', days);
  25  		setElement('countdown-hours', hours);
  26  		setElement('countdown-minutes', minutes);
  27  		setElement('countdown-seconds', seconds);
  28  		
  29  		countdown.timer = setTimeout(countdown, 1000);
  30  	}
  31  	
  32  		
  33  	function start() {
  34  		this.timer = setTimeout(countdown, 1000);
  35  	}
  36  	
  37  	start(then);	
  38  }
  39  
  40  Countdown(new Date("Dec 04 2008 12:00:00"));

Required HTML:

   1  <span id="countdown-days"></span> days
   2  
   3  <span id="countdown-hours"></span>:<span id="countdown-minutes"></span>:<span id="countdown-seconds"></span>

Output is for example:

   1  23 days 23:00:12