1.Wxml

<!-- 日历年月 -->
<view class='calendar_title flex_nowrap'>
  <view class='icon' bindtap='lastMonth'>
    <image src='/images/icon/28.png' />
  </view>
  <view>{{year}}年{{month}}月</view>
  <view class='icon' bindtap='nextMonth'>
    <image src='/images/icon/29.png' />
  </view>
</view>

<!-- 日历主体 -->
<view class='calendar'>
  <view class='header'>
    <view wx:for='{{date}}' wx:key='' class='{{(index == todayIndex) && isTodayWeek ? "weekMark" : ""}}'>{{item}}
      <view></view>
    </view>
  </view>

  <view class='date-box'>
    <block wx:for='{{dateArr}}' wx:key=''>
      <view class='{{isToday == item.isToday ? "nowDay" : ""}}'>
        <view class='date-head' bindtap='lookHuoDong' data-year='{{year}}' data-month='{{month}}' data-datenum='{{item.dateNum}}'>
          <view>{{item.dateNum}}</view>
        </view>
      </view>
    </block>
  </view>

</view>

2.Js

Page({
  data: {
    year: 0,
    month: 0,
    date: ['日', '一', '二', '三', '四', '五', '六'],
    dateArr: [],
    isToday: 0,
    isTodayWeek: false,
    todayIndex: 0
  },
  onLoad: function () {
    let now = new Date();
    let year = now.getFullYear();
    let month = now.getMonth() + 1;
    this.dateInit();
    this.setData({
      year: year,
      month: month,
      isToday: '' + year + month + now.getDate()
    })
  },
  dateInit: function (setYear, setMonth) {
    //全部时间的月份都是按0~11基准，显示月份才+1
    let dateArr = [];                       //需要遍历的日历数组数据
    let arrLen = 0;                         //dateArr的数组长度
    let now = setYear ? new Date(setYear, setMonth) : new Date();
    let year = setYear || now.getFullYear();
    let nextYear = 0;
    let month = setMonth || now.getMonth();                 //没有+1方便后面计算当月总天数
    let nextMonth = (month + 1) > 11 ? 1 : (month + 1);
    let startWeek = new Date(year + ',' + (month + 1) + ',' + 1).getDay();                          //目标月1号对应的星期
    let dayNums = new Date(year, nextMonth, 0).getDate();               //获取目标月有多少天
    let obj = {};
    let num = 0;
    if (month + 1 > 11) {
      nextYear = year + 1;
      dayNums = new Date(nextYear, nextMonth, 0).getDate();
    }
    arrLen = startWeek + dayNums;
    for (let i = 0; i < arrLen; i++) {
      if (i >= startWeek) {
        num = i - startWeek + 1;
        obj = {
          isToday: '' + year + (month + 1) + num,
          dateNum: num,
          weight: 5
        }
      } else {
        obj = {};
      }
      dateArr[i] = obj;
    }
    this.setData({
      dateArr: dateArr
    })
    let nowDate = new Date();
    let nowYear = nowDate.getFullYear();
    let nowMonth = nowDate.getMonth() + 1;
    let nowWeek = nowDate.getDay();
    let getYear = setYear || nowYear;
    let getMonth = setMonth >= 0 ? (setMonth + 1) : nowMonth;
    if (nowYear == getYear && nowMonth == getMonth) {
      this.setData({
        isTodayWeek: true,
        todayIndex: nowWeek
      })
    } else {
      this.setData({
        isTodayWeek: false,
        todayIndex: -1
      })
    }
  },
  /**
   * 上月切换
   */
  lastMonth: function () {
    //全部时间的月份都是按0~11基准，显示月份才+1
    let year = this.data.month - 2 < 0 ? this.data.year - 1 : this.data.year;
    let month = this.data.month - 2 < 0 ? 11 : this.data.month - 2;
    this.setData({
      year: year,
      month: (month + 1)
    })
    this.dateInit(year, month);
  },
  /**
   * 下月切换
   */
  nextMonth: function () {
    //全部时间的月份都是按0~11基准，显示月份才+1
    let year = this.data.month > 11 ? this.data.year + 1 : this.data.year;
    let month = this.data.month > 11 ? 0 : this.data.month;
    this.setData({
      year: year,
      month: (month + 1)
    })
    this.dateInit(year, month);
  }
})

3.Wxss

.calendar_title{width: 70%; margin: 10rpx auto; justify-content: space-between;font-size: 20pt;color: #fff;}
.calendar_title .icon image{width: 60rpx; height: 60rpx;margin: 5rpx auto;}

/* 日历 */
.calendar{width: 100%;margin-top: 75rpx;background: #fff;border-bottom-right-radius: 20rpx;border-bottom-left-radius: 20rpx;padding: 0 0 20rpx;font-family: FZZhunYuan-M02S;}
.header{font-size: 0;width: 80%;margin: 0 auto;}
.header>view{display: inline-block;width: 14.285%;color: #666;font-size: 30rpx;text-align: center;border-bottom: 1px solid #D0D0D0;padding: 20rpx 0;}
.weekMark{position: relative;width: 80%;margin: 0 auto;}
.weekMark view{position: absolute;bottom: 0;left: 0;width: 100%;border-bottom: 2px solid #69f;}
.date-box{font-size: 0;padding: 10rpx 0;width: 80%;margin: 0 auto;}
.date-box>view{position: relative;display: inline-block;width: 14.285%;color: #666;text-align: center;vertical-align: middle;}
.date-head{height: 60rpx;line-height: 60rpx;font-size: 12pt;}
.nowDay .date-head{width: 60rpx;border-radius: 50%;text-align: center;color: #fff;background-color: #ff9933;margin: 0 auto;}

日历效果图

PS：上面图中为在实际项目中的日历效果，上述代码则无蓝色波浪效果。