normalizeValue(value) {
      const firstDateTimestamp = this._extractFirstTimestamp(value);
      const lastDateTimestamp = this._extractLastTimestamp(value);
      if (firstDateTimestamp && lastDateTimestamp && firstDateTimestamp > lastDateTimestamp) {
        // if both are timestamps (not undefined), flip if necessary
        return this._buildValue(lastDateTimestamp, firstDateTimestamp);
      }
      return this._buildValue(firstDateTimestamp, lastDateTimestamp);
    }
Extract both dates as timestamps, flip if necessary, and build (which will use the desired format so we enforce the format too)
@override