/**
 * CountDown Class
 *
 * @author		Giovambattista Fazioli
 * @email		 [email protected]
 * @web		   http://www.undolog.com
 *
 * @param	dd   (string) 'month day, year'
 *
 */
function countDown( dd ) {
	// init target time
	var target			= new Date( dd );
	this.targetTime		= target.getTime();
	/**
	 * refresh countdown
	 */
	this.refresh = function() {
		var today				 = new Date();
		var currentTime		   = today.getTime();
		// time left
		this._leftMilliseconds	= (this.targetTime - currentTime);
		this._leftSeconds		 = Math.floor( this._leftMilliseconds / 1000 );
		this._leftMinutes		 = Math.floor( this._leftSeconds / 60 );
		this._leftHours		   = Math.floor( this._leftMinutes / 60 );
		// no module
		this.leftDays			 = Math.floor( this._leftHours / 24 );
		// for print
		this.leftMilliseconds	 = this._leftMilliseconds % 1000;
		this.leftSeconds		  = this._leftSeconds % 60;
		this.leftMinutes		  = this._leftMinutes % 60;
		this.leftHours			= this._leftHours % 24;
	}
	this.refresh();
}

http://www.undolog.com/2008/10/13/una-classe-countdown-in-javascript/

A simple countDown class in Javascript:

countDown Class in Javascript

javascript, class

JavaScript