Today is Koninkrijksdag, on this day in 1954 the Queen Juliana signed the charter that detailed the relationship between it's self and several of it's over seas territories. Since then several others have also been added to this charter.
In recognition of the day a concert is held each year with musicions from all over the kingdom. Many people consider today to be a flag day where it is appropriate to show pride in the Kingdom of the Netherlands by raising the flag and flying it today.
In 2008 Naturalisatiedag was moved from October 1 to December 15 bringing further significance to the day. This is the day when all naturalized individuals receive their office certificate showing they are Dutch citizens.
Links:http://en.wikipedia.org/wiki/Koninkrijksdag