Koninginnedag, meaning Queen’s Day, is a national holiday in the Netherlands that is also celebrated with great energy in New York and other places around the globe.

It falls on April 30th, unless that happens to be a Sunday, in which case it falls on the 29th. The holiday is Queen Beatrix’s “official celebration day” (Wikipedia’s term, anyway), but I’m afraid I know about it myself mostly just from seeing people around town in orange clothing!