js 倒计时

     var interval = 1000; 
        function ShowCountDown(year,month,day,divname) 
        { 
            var now = new Date();   
            alert(now)
            var endDate = new Date(year, month-1, day); 
            alert(endDate)
            var leftTime=endDate.getTime()-now.getTime(); 
            alert(leftTime)
            var leftsecond = parseInt(leftTime/1000); 
                       var day1=Math.floor(leftsecond/(60*60*24)); 
            var hour=Math.floor((leftsecond-day1*24*60*60)/3600); 
            var minute=Math.floor((leftsecond-day1*24*60*60-hour*3600)/60); 
            var second=Math.floor(leftsecond-day1*24*60*60-hour*3600-minute*60); 
            var cc = document.getElementById(divname); 
            cc.innerHTML = "3.15距离"+year+"年"+month+"月"+day+"日还有："+day1+"天"+hour+"小时"+minute+"分"+second+"秒"; 
        } 
        window.setInterval(function(){ShowCountDown(2014,3,15,'divdown1');}, interval);