廢話不多說直接上程式碼：

效果圖：

index.js

Page({

  /**
   * 頁面的初始資料
   */
  data: {
    countdown:''
,    endDate2: '2018-08-08 11:41:00'
  },
  /**
   * 生命週期函式--監聽頁面載入
   */
  onLoad: function (options) {
    var that = this;
    that.countTime()
  },
  countTime() {
    var that = this;
    var date = new Date();
    var now = date.getTime();
    var endDate = new Date(that.data.endDate2);//設定截止時間
    var end = endDate.getTime();
    var leftTime = end - now; //時間差                              
    var d, h, m, s, ms;
    if (leftTime >= 0) {
      d = Math.floor(leftTime / 1000 / 60 / 60 / 24);
      h = Math.floor(leftTime / 1000 / 60 / 60 % 24);
      m = Math.floor(leftTime / 1000 / 60 % 60);
      s = Math.floor(leftTime / 1000 % 60);
      ms = Math.floor(leftTime % 1000);
      ms = ms < 100 ? "0" + ms : ms
      s = s < 10 ? "0" + s : s
      m = m < 10 ? "0" + m : m
      h = h < 10 ? "0" + h : h
      that.setData({
        countdown: d + "：" + h + "：" + m + "：" + s + ":" + ms,
      })
     //遞迴每秒呼叫countTime方法，顯示動態時間效果
    setTimeout(that.countTime, 100);
    } else {
      console.log('已截止')
      that.setData({
        countdown:'00:00:00'
      })
    }
   
  },
})
 

index.html

<view>
    <text>{{countdown}}</text>
</view>