jquery 倒计时效果

function daojishi(){
            var starttime = new Date("2017-09-30 01:06:11");
            //date的格式也可以写成："2017/09/30 01:06:11"
            //其他格式还没试过
	  	setInterval(function () {
	    var nowtime = new Date();
	    var time = starttime - nowtime;
	    var day = parseInt(time / 1000 / 60 / 60 / 24);
	    var hour = parseInt(time / 1000 / 60 / 60 % 24);
	    var minute = parseInt(time / 1000 / 60 % 60);
	    var seconds = parseInt(time / 1000 % 60);
	    if (day<0 || hour<0 || minute<0 || seconds<0) {
	    	day =0;
	    	hour =0;
	    	minute =0;
	    	seconds =0;
	    }
	    $(".day").html(day);
	    $(".hour").html(hour);
	    $(".min").html(minute);
	    $(".sec").html(seconds);
 
	  }, 1000);
}