javascript实现抢购倒计时程序

<div id="clientclock">  </div>  <br />  <br />  <br />  <br />  <mce:script type="text/javascript"><!--  //抢票起始时间 2011年2月29日10点10分0秒，月份的定义从0开始，因此1表示2月份。  var start = new Date('2011', '1', '29', '10', '10', '00');  //var start = new Date('2011','1', '28', '15', '10', '00');   //抢票截止时间 2011年2月29日11点10分59秒  var expire = new Date('2011', '1', '29', '11', '10', '59');   //显示倒计时的HTML对象  var clock = document.getElementById('clientclock');   //倒计时函数，每秒执行一次  setLeftTime();   function setLeftTime() {   var now = new Date();   //如果当前时间小于抢票起始时间，那么显示：抢票倒计时××天××时××分××秒  if (now < start) {  var diff = -480 - now.getTimezoneOffset() //是北京时间和当地时间的时间差  var lefttime = (start.getTime() - now.getTime()) + diff * 60000  var day = Math.floor(lefttime / (1000 * 60 * 60 * 24));  var hour = Math.floor(lefttime / (1000 * 3600)) - (day * 24);  var minute = Math.floor(lefttime / (1000 * 60)) - (day * 24 * 60) - (hour * 60);  var second = Math.floor(lefttime / (1000)) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60);   clock.innerHTML = '抢票倒计时：<span class="ztCopy">' + day + '</span>天 <span class="ztCopy">' + hour + '</span>时 <span class="ztCopy">' + minute + '</span>分 <span class="ztCopy">' + second + '</span>秒';  }  //如果当前时间大于等于抢票起始时间，小于抢票截止时间，即：正在抢票，那么显示：抢票还剩××天××时××分××秒  else if (now <= expire) {  var diff = -480 - now.getTimezoneOffset() //是北京时间和当地时间的时间差  var lefttime = (expire.getTime() - now.getTime()) + diff * 60000  var day = Math.floor(lefttime / (1000 * 60 * 60 * 24));  var hour = Math.floor(lefttime / (1000 * 3600)) - (day * 24);  var minute = Math.floor(lefttime / (1000 * 60)) - (day * 24 * 60) - (hour * 60);  var second = Math.floor(lefttime / (1000)) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60);   clock.innerHTML = '抢票还剩：<span class="ztCopy">' + day + '</span>天 <span class="ztCopy">' + hour + '</span>时 <span class="ztCopy">' + minute + '</span>分 <span class="ztCopy">' + second + '</span>秒';  }  //如果当前时间大于抢票截止时间，即：本轮抢票结束，那么显示：本轮抢购结束  else {  clock.innerHTML = '本轮抢购结束';  }   setTimeout("setLeftTime()", 1000);  } // --></mce:script>