The dates of commemoration of WWII in Holland are May 4th and May 5th. At 8
pm on May 4th 2 minutes of silence are observed throughout the country.
During the day, it's business as usual. May 5th is the day of liberation,
but is now only observed as a nationwide holiday every five years. So, this
year everything is open as on any other day. The other day to remember is
April 30, queen's birthday (though the current queen Beatrix has her
birthday January 31st). For reasons of weather, Beatrix decided to keep her
mother's birthday as a national holiday. It's very worth while to visit
Holland on April 30. In Amsterdam there's a gigantic fleamarket; everyone
seems to clean out their attic and garage, or tries to resell the stuff they
bought the year before.
April, to my mind is a wonderful month to visit the country, despite
uncertain weather. The tulip fields around Lisse are ablaze, de Keukenhof,
the annual flower exhibition, is at its peak.