h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The thing that comes to mind immediately is the celebration of Queen's Day. It's a major celebration, which is being held throughout the entire country. It has always been the celebration of the Queen's birthday.
Queen's Day has been celebrated in Holland for over a century now. It started with Queen Wilhelmina in 1898. Her birthday was august 31, and that day has been the official date for 50 years. After that, Juliana became queen in 1948, and since her birthday was (is) at april 30, Queen's Day has been moved to a different date. Since 1980 (not sure about the actual year), Beatrix has been queen, and her birthday is January 31. However, she decided that she did not want the date to change again, so Queen's Day remained at april 30.

The day always includes a visit to a "random" town or city by the entire royal family with big media coverage and big parties everywhere in the country. When asked where one should celebrate Queen's Day, most people will respond: Amsterdam.
Every year, the city is filled with people from all over the country to visit the concerts, dance events or just take a walk in the city centre and do a bit of shopping.

Of course, Amsterdam is not the only place, almost every town has special events like a big market, concerts, fancy-fair kind of things and so on. The colour of the day is orange, and it can be seen whenever one opens his/her eyes.