SOURCE

function FreshTime() {
  var endtime = new Date("2017/6/17,10:09:00"); //结束时间
  var nowtime = new Date(); //当前时间
  var lefttime = parseInt((endtime.getTime() - nowtime.getTime()) / 1000);

  d = parseInt(lefttime / (24 * 60 * 60));
  h = parseInt(lefttime / (60 * 60) % 24);
  m = parseInt(lefttime / 60 % 60);
  s = parseInt(lefttime % 60);
  document.getElementById("LeftTime").innerHTML = d + "天" + h + "小时" + m + "分" + s + "秒";
  if (lefttime <= 0) {
    document.getElementById("LeftTime").innerHTML = "团购已结束";
    clearInterval(sh);
  }
}
FreshTime();
var sh;
sh = setInterval(FreshTime, 500);

<div class="content3">
  <div class="time">
    还剩
    <span id="LeftTime">
    </span>
  </div>
</div>