This is a national holiday declared in 2014 to maintain the tradition of a holiday to celebrate the monarch of the Netherlands.
It is celebrated annually on 27 April, unless it falls on a Sunday, in which case Saturday 26 April will be the observed holiday.
The day officially commemorates the birthday of Willem Alexander who became King of the Netherlands following the abdication of Queen Beatrix on 30 April 2013.
The royal palace has announced that to celebrate his 50th birthday in 2017, the king will invite 150 people to dine with him and his wife, Queen Maxima, at their palace in Amsterdam.
A website has been set up at www.WA50.nl for those hoping to win an invitation, and the lucky 150 guests will be chosen in a lottery on 3 March.
The draw is open only to those who share the king's birthday, live in The Netherlands, are over 20 and who are celebrating a 'jubilee year' - a birthday which is divisible by five, the palace said in a statement.
The tradition of a holiday to honour the current monarch began before the World War II. Initially it celebrated the birthday of Queen Wilhelmina on 31 August.
Since 1949, the day has celebrated of the birthday of Wilhelmina's daughter, Queen Juliana, on 30 April.
The tradition of changing the holiday to match the birthday of the reigning queen stopped when Queen Beatrix succeeded Juliana in 1980.
Beatrix decided to keep that the Queen's Day on April 30 as a tribute to her mother. Additionally her own birthday is at the end of January 31, so celebrating it outdoors would be difficult.
Traditionally, on this day the King visits one of the cities in the country, and meets celebrating people.
On King's day many people will celebrate by dressing in orange clothes (the royal family are the House of Orange), painting faces and hair orange and wearing mock orange crowns.
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