private function buildUrl(DateTimeInterface $requestedDate = null): string
    {
        if (null === $requestedDate) {
            $fileName = 'today';
        } else {
            $yearMonth = $requestedDate->format('Ym');
            $dayMonthYear = $requestedDate->format('dmY');
            $fileName = "$yearMonth/$dayMonthYear";
        }

        return self::BASE_URL.$fileName.self::FILE_EXTENSION;
    }