late Feb: Holland Flowers Festival, a must-see garden show that takes place at the Greenery complex, covering 4, 500 sq. m in Wervershoof; this event is known for its creative landscape designs on display.
March: TEFAF Maastricht, the European Fine Art Fair, one of the world’s leading art and antiques fairs that attracts dealers and collectors globally.
April 30: Queen’s Day (Koninginnedag), a national celebration with massive, mad street party in Amsterdam. It is also known as Orange day and many people wander about dressed in orange, the royal colour representing the House of Orange.
late May/June: Holland Festival, Netherlands’ largest performing arts festival held mainly in Amsterdam and The Hague since 1947.
The 2nd weekend of July: North Sea Jazz Festival, one of the best and arguably the biggest jazz event in the world, with world-class artists and 23, 000 visitors a day. Previously held in the Hague, it has been held in Rotterdam since 2006. 3 days.
The first weekend of August: Amsterdam Pride is one of Europe’s largest gay/lesbian festivals. The world famous Canal Parade, with a hundred decorated boats and music, is a must-see.
For some precise dates, more suggestions and information see European Festivals or Arts Festivals