Gets a list of all official holidays in Belgium

BeHolidays.php

<?php
use DateTimeImmutable;
use DateInterval;
use DateTimeZone;
use IteratorAggregate;
use ArrayIterator;

class BeHolidays implements IteratorAggregate
{

    protected static $years = [];
    protected $year;
    protected $easter;
    protected $list;
    protected $timezone;

    public static function get(int $year = null):BeHolidays
    {
        $year = $year??date('Y');
        if (!array_key_exists($year, static::$years)) {
            static::$years[$year] = new BeHolidays($year);
        }
        return static::$years[$year];
    }

    protected function __construct(int $year)
    {
        $this->year = $year;

        $this->timezone = new DateTimeZone("Europe/Brussels");
        $days = easter_days($this->year);
        $this->easter = $this->makeDate(3, 21)->add(new DateInterval("P{$days}D"));
        $this->list = $this->generateList();
    }


    public function getEaster(): DateTimeImmutable
    {
        return $this->easter;
    }

    protected function makeDate(int $month, int $day):DateTimeImmutable
    {
        return new DateTimeImmutable("{$this->year}-{$month}-{$day} 00:00:00", $this->timezone);
    }

    protected function generateList():array
    {
        $list = [
            [
                "date" => $this->makeDate(1, 1),
                "name" => [
                    "nl" => "Nieuwjaar",
                    "fr" => "Nouvel an",
                    "de" => "Neujahr",
                    "en" => "New Year's day"
                ]
            ],
            [
                "date" => $this->makeDate(5, 1),
                "name" => [
                    "nl" => "Dag van de arbeid",
                    "fr" => "Fête du travail",
                    "de" => "Tag der Arbeit",
                    "en" => "Labour day"
                ]
            ],
            [
                "date" => $this->makeDate(7, 21),
                "name" => [
                    "nl" => "Nationale feestdag",
                    "fr" => "Fête Nationale",
                    "de" => "Nationalfeiertag",
                    "en" => "Belgian National Day"
                ]
            ],
            [
                "date" => $this->makeDate(8, 15),
                "name" => [
                    "nl" => "Onze-Lieve-Vrouw-Hemelvaart",
                    "fr" => "Assomption",
                    "de" => "Mariä Himmelfahrt",
                    "en" => "Assumption of Mary"
                ]
            ],
            [
                "date" => $this->makeDate(11, 1),
                "name" => [
                    "nl" => "Allerheiligen",
                    "fr" => "Toussaint",
                    "de" => "Allerheiligen",
                    "en" => "All Saint's day"
                ]
            ],
            [
                "date" => $this->makeDate(11, 11),
                "name" => [
                    "nl" => "Wapenstilstand",
                    "fr" => "Jour de l'Armistice",
                    "de" => "Waffenstillstand",
                    "en" => "Armisitice Day"
                ]
            ],
            [
                "date" => $this->makeDate(12, 25),
                "name" => [
                    "nl" => "Kerstmis",
                    "fr" => "Noël",
                    "de" => "Weihnachten",
                    "en" => "Christmas"
                ]
            ]
        ];

        $list[] = [
            "date" => $this->easter->add(new DateInterval("P1D")),
            "name" => [
                "nl" => "Paasmaandag",
                "fr" => "Lundi de Pâques",
                "de" => "Ostermontag",
                "en" => "Easter Monday"
            ]
        ];
        $list[] = [
            "date" => $this->easter->add(new DateInterval("P39D")),
            "name" => [
                "nl" => "Onze-Lieve-Heer-Hemelvaart",
                "fr" => "Ascension",
                "de" => "Christi Himmelfahrt",
                "en" => "Ascension"
            ]
        ];
        $list[] = [
            "date" => $this->easter->add(new DateInterval("P50D")),
            "name" => [
                "nl" => "Pinkstermaandag",
                "fr" => "Lundi de Pentecôte",
                "de" => "Pfingstmontag",
                "en" => "Pentecost Monday"
            ]
        ];


        usort($list, function ($a, $b) {
            return $a['date']<=>$b['date'];
        });

        $this->list = [];
        array_map(function ($item) {
            $this->list[$item["date"]->format("m-d")] = $item;
        }, $list);
        return $this->list;
    }

    public function getIterator():ArrayIterator
    {
        return new ArrayIterator($this->list);
    }

    public function toArray():array
    {
        return $this->list;
    }

    public function isHoliday(int $month, int $day)
    {
        $key = $this->makeDate($month, $day)->format("m-d");
        return array_key_exists($key, $this->list);
    }

}