element-ui 时间格式 value-format="yyyy-MM-dd" value-format="yyyy-MM-dd hh:mm:ss"

                <el-date-picker
                  v-model="createTime"
                  type="daterange"
                  range-separator="至"
                  start-placeholder="开始日期"
                  end-placeholder="结束日期"
                  value-format="yyyy-MM-dd"
                  :picker-options="pickerOptions"
                  @change="getStime">
                </el-date-picker>
              </el-form-item>

注意：hh 为12小时制
     HH 为24小时制
          <el-form-item label="下单时间：">
                <el-date-picker
                  v-model="createTime"
                  type="datetimerange"
                  range-separator="至"
                  start-placeholder="开始日期"
                  end-placeholder="结束日期"
                  value-format="yyyy-MM-dd HH:mm:ss" 
                  :default-time="['00:00:00', '23:59:59']"
                  :time-arrow-control="true"
                  :picker-options="pickerOptions"
                  @change="getStime">
                </el-date-picker>
              </el-form-item>