代码：

js:

function countDown(time, id) {  //time的格式yyyy/MM/dd hh:mm:ss
    var day_elem = $(id).find('.day');
    var hour_elem = $(id).find('.hour');
    var minute_elem = $(id).find('.minute');
    var second_elem = $(id).find('.second');
    var end_time = new Date(time).getTime(), //月份是实际月份-1
    sys_second = (end_time - new Date().getTime()) / 1000;
    var timer = setInterval(function () {
        if (sys_second > 1) {
            sys_second -= 1;
            var day = Math.floor((sys_second / 3600) / 24);
            var hour = Math.floor((sys_second / 3600) % 24);
            var minute = Math.floor((sys_second / 60) % 60);
            var second = Math.floor(sys_second % 60);
            day_elem && $(day_elem).text(day); //计算天
            $(hour_elem).text(hour < 10 ? "0" + hour : hour); //计算小时
            $(minute_elem).text(minute < 10 ? "0" + minute : minute); //计算分钟
            $(second_elem).text(second < 10 ? "0" + second : second); //计算秒杀
        } else {
            clearInterval(timer);
        }
    }, 1000);
}

html:

　　<p id="colockbox">
              <span class="day" id="day">00</span>

　　　　　<span class="hour">00</span>:

<span  class="minute">24</span>:

　　　　　<span class="second">24</span>
      </p>