King's Day (Netherlands, Aruba, Curaçao, Sint Maarten) (celebrated on April 26 if April 27 falls on a Sunday)

Koningsdag or King's Day is a national holiday in the Kingdom of the Netherlands. Celebrated on 27 April, the date marks the birth of King Willem-Alexander. When the Dutch monarch is female, the holiday is known as Koninginnedag ( ) or Queen's Day and, under Queen Beatrix until 2013, was celebrated on 30 April. She prolonged the tradition that was born under her mother's reign: Queen Juliana's birthday was on 30 April.

Aruba, officially the Country of Aruba, is a constituent island country within the Kingdom of the Netherlands, in the southern Caribbean Sea 29 kilometres (18 mi) north of the Venezuelan peninsula of Paraguaná and 80 kilometres (50 mi) northwest of Curaçao. In 1986, Aruba became a constituent country within the Kingdom of the Netherlands and acquired the formal name the Country of Aruba.

Curaçao, officially the Country of Curaçao, is a constituent island country within the Kingdom of the Netherlands, located in the southern Caribbean Sea, about 65 km (40 mi) north of Venezuela.

Sint Maarten is a constituent country of the Kingdom of the Netherlands located in the Caribbean region of North America. With a population of 58,477 as of June 2023 on an area of 34 km² (13 sq mi), it encompasses the southern 44% of the divided island of Saint Martin, while the northern 56% of the island constitutes the French overseas collectivity of Saint Martin. Sint Maarten's capital is Philipsburg. Collectively, Sint Maarten and the other Dutch islands in the Caribbean are often called the Dutch Caribbean.