My last column was about Dutch birthdays, but there is one birthday I should not forget — and that is the Dutch queen's birthday (Koninginnedag, or Queen's Day).

On April 30, the whole of Amsterdam and other cities in Holland become like a mass flea market because people are allowed to celebrate the national day in a way they like best: indulging in free trade and making money while getting rid of unwanted stuff.

And all this without paying taxes, owing to a holiday dispensation favor by the Dutch government.

This day, to be precise, is not the birthday of Queen Beatrix but that of her mother, the former Queen Juliana. When she ascended to the throne, Queen Beatrix decided to keep the April 30 holiday as a tribute to her mother. Queen Beatrix's Jan. 31 birthday falls in the coldest period in Holland — not suitable for a celebration that involves many street parties and outdoor events.

If anyone has a chance to visit Holland, I would highly recommend including this day in the plan, though hotels must be booked well in advance and one should not arrive on the day itself. Access with luggage anywhere will be difficult with everybody selling everything everywhere.

It is a truly impressive and fun-filled day, with people and streets adorned with the national orange color, which derives from the royal family's name, House of Orange-Nassau.

There are special events for children, bands play everywhere and — with of course space cakes and pot on sale — masses of people dance at every street corner.

But the most impressive aspect of Queen's Day for me is the creativity of the people.

Because the articles for sale are not restricted to commodities and are left to people's imagination, many, especially children, come up with great ideas — such as by paying 0.50 euro, one can look into a box labeled "MONSTER," only to find out that a mirror is stuck at its bottom.

Another fun idea I saw this year, also sold by children, was a cardboard cutout of U.S. President Barack Obama, and for a euro one could have one's photo taken with the cutout and have it sent by e-mail.

I once heard that many successful Dutch entrepreneurs had experience running such stands as children on Queen's Day, which is very convincing.

But despite the fun, Queen's Day 2009 unfortunately ended in tragedy, when a 38-year-old driver crashed through a parade in the city of Apeldoorn, killing eight, including himself, while narrowly missing an open-top bus carrying the royal family.

Unlike her predecessors, who mainly received guests at their residence on their birthdays, Queen Beatrix goes out and meets the people on Queen's Day, visiting over 50 areas in Holland since she became the queen in 1980. Known to be open and accessible, she has also been reported casually going shopping and riding bicycles.

But all this will now have to change.

Although his motives remain unclear, police reported that, prior to his death, the attacker said it was a "deliberate act aimed at the royal family."

Holland has long been quite a peaceful country. But security, which used to be relaxed, has been heightened in recent years as right-wing politician Pim Fortuyn and film director Theo van Gogh, both critical of Islam, were murdered on the streets in 2002 and 2004, respectively.

With this latest incident on Queen's Day, the idyllic scene of the queen casually going shopping will unfortunately be a thing of the past.