_modifyDateValue(amount, unit, preserveDate) {
      if (!this.dateValue) {
        return;
      }
      const modifiedDate = (0, _modifyDateBy.default)(_CalendarDate.default.fromLocalJSDate(this.dateValue), amount, unit, preserveDate, this._minDate, this._maxDate);
      const newValue = this.formatValue(modifiedDate.toUTCJSDate());
      this._updateValueAndFireEvents(newValue, true, ["change", "value-changed"]);
    }
@param { number } amount
@param { string } unit
@param { boolean } preserveDate whether to preserve the day of the month (f.e. 15th of March + 1 month = 15th of April)
@protected