微信小程序pinker组件使用实现自动相减日期

<view class="section">
   <view class="section__title">开始时间</view>
   <picker mode="date" value="{{date}}" start="{{startTime}}" end="2020-09-01" bindchange="bindDateChange">
    <view class="picker">
     <text>{{date}}</text>
     <image src="/images/three.png"></image>
    </view>
   </picker>
  </view>

  <view class="section">
   <view class="section__title">结束时间</view>
   <picker mode="date" value="{{date2}}" start="{{date}}" end="2050-09-01" bindchange="bindDate2Change">
    <view class="picker">
     <text>{{date2}}</text>
     <image src="/images/three.png"></image>
    </view>
   </picker>
  </view>

  //获取当前时间戳 
  var timestamp = Date.parse(new Date());
  timestamp = timestamp / 1000;
  console.log("当前时间戳为" + timestamp);

  //获取当前时间 
  var n = timestamp  1000;
  var date = new Date(n);
  //年 
  var Y = date.getFullYear();
  //月 
  var M = (date.getMonth() + 1 < 10 ? '0' + (date.getMonth() + 1) : date.getMonth() + 1);
  //日 
  var D = date.getDate() < 10 ? '0' + date.getDate() : date.getDate();
  //天
  var H = date.getHours(); 
  //时 
  var m = date.getMinutes(); 
  //分 
  var time = Y + "-" + M + "-" + D;
  var time2 = Y + "-" + M + "-" + D + "-" + H + ":" + m;
  console.log(time)
  console.log(time2)

// 获取开始时间、结束时间,相减
  var start_date = new Date(this.data.date.replace(/-/g, "/"));
  var end_date = new Date(this.data.date2.replace(/-/g, "/"));
  var days = end_date.getTime() - start_date.getTime();
  var day = parseInt(days / (1000  60  60  24));
  console.log(day);
  if (day > 0) {
   this.setData({
    num: day
   })
  } else if (day == 0) {
   this.setData({
    num: 1
   })
  } else if (day < 0) {
   this.setData({
    date2:''
   })
  }
 },

 <view class="infoDiv">
   <text>请假时长</text>
   <view wx:if="{{date2&&date}}">
    <input auto-focus placeholder="" type="text" value="{{num+'天'}}" disabled="disabled" bindchange="num_data" />
   </view>
   <view wx:else="">
    <input auto-focus placeholder="" type="text" value="" bindchange="num_data" disabled="disabled" />
   </view>

  </view>