微信小程序picker日期选择器start和end无效？

Question

 <view class="weui-cells weui-cells_after-title">        <view class="weui-cell weui-cell_input">          <view class="weui-cell__hd">            <view class="weui-label">当前选择</view>          </view>          <view class="weui-cell__bd">            <picker mode="date" value="{{date}}" start="2015-09-01" end="2017-09-01" bindchange="bindDateChange">              <view class="weui-input">{{date}}</view>            </picker>          </view>        </view>      </view>