function Countdown(then) {
     
     	this.then = then;
     	
     	function setElement(id, value) {
     		if (value.length < 2) {
     	    	value = "0" + value;
     		}
     	
    		window.document.getElementById(id).innerHTML = value;
    	}
    	
    	function countdown() {
    		now  		  = new Date();
    	  	diff		  = new Date(this.then - now);
    	  	
    		seconds_left  = Math.floor(diff.valueOf() / 1000);
    	
    		seconds  = Math.floor(seconds_left / 1) % 60;
    		minutes  = Math.floor(seconds_left / 60) % 60;
    		hours    = Math.floor(seconds_left / 3600) % 24;
    		days     = Math.floor(seconds_left / 86400) % 86400;
    		if (hours<0)
		{		
			seconds = 0;
			minutes = 0;
			hours = 0;
			days = 0 ;
		}	
    		setElement('countdown-days', days);
    		setElement('countdown-hours', hours);
    		setElement('countdown-minutes', minutes);
    		setElement('countdown-seconds', seconds);
    		
    		countdown.timer = setTimeout(countdown, 1000);
    	}
    	
    		
    	function start() {
    		this.timer = setTimeout(countdown, 1000);
    	}
    	
   	start(then);	
    }