Queen's Day (Koninginnedag) in Amsterdam

Koninginnedag or Queen's Day was a national holiday in the Kingdom of the Netherlands until 2013. Celebrated on April 30, Koninginnedag was Queen Beatrix's official day of celebration. Although Queen Beatrix was born on January 31, the holiday is celebrated on April 30 because it was the birthday of her mother and predecessor, Juliana. Many traditional activities take place outdoors, and the observation of vacations in April makes favorable weather more likely. From 2014, the holiday is to be known as Koningsdag or King's Day following the investiture of Willem-Alexander as King of the Netherlands on April 30, 2013. It is to be celebrated on Willem-Alexander's birthday, April 27.

 Everyone wears orange, and so should you 

Orange is worn on King's Day as a sign of pride for the Dutch royal family. So raid your wardrobe, your friends' wardrobes, your local charity store and anywhere else you can think of for orange clothes and accessories, and wear them with pride. If you're not covered head-to-toe in orange on King's Day, you're not doing it right. Orange wigs and face paint are also popular - the wackier, the better. Yes, you'll look like a fool. But fortunately, so will everyone else.