public function add(Holiday $holiday)
    {
        if (-1 !== $index = $this->getIndexByNameAndDate($holiday->getName(), $holiday->getDate())) {
            $this->holidayList[$index] = new Holiday($holiday->getName(), $holiday->getDate(), $holiday->getType() | $this->holidayList[$index]->getType());
        } else {
            $this->holidayList[] = $holiday;
        }
    }