只上核心代码

      <el-form-item label="计划时间" width="100px">
                <el-date-picker
                  v-model="palanTime"
                  type="datetimerange"
                  range-separator="至"
                  start-placeholder="开始日期"
                  end-placeholder="结束日期"
                  format="yyyy-MM-dd HH:mm:ss"
                  >
                </el-date-picker>
              </el-form-item>


  watch: {
    palanTime(val) {
      if (val) {
        this.form.params.planbeginTime = this.getDateTime(val[0]);
        this.form.params.planendTime = this.getDateTime(val[1]);
      } else {
        this.form.params.planbeginTime = null
        this.form.params.planendTime = null
      }
    }
  },

    // 表单参数
      form: {
        params: {
          planbeginTime: null,
          planendTime: null
        }
      },




  methods: {
    getDateTime(chinaStandard) {
      var date = new Date(chinaStandard);
      var y = date.getFullYear();
      var m = date.getMonth() + 1;
      m = m < 10 ? ('0' + m) : m;
      var d = date.getDate();
      d = d < 10 ? ('0' + d) : d;
        var h = date.getHours();
      h = h < 10 ? ('0' + h): h;
      var minute = date.getMinutes();
      minute = minute < 10 ? ('0' + minute) : minute;
      let s = date.getSeconds();
      s = s < 10 ? ('0' + s): s;
      return y + '-' + m + '-' + d + ' ' + h + ':' + minute + ':' + s;  //这里如果不需要小时 分  后边的可以不需要拼接
    },

效果