In June of each year, the streets of Denmark are suddenly full of young people wearing stiff white caps with bands of various colors - burgundy, midnight blue, light blue. These teenagers have just graduated from gymnasium, the Danish equivalent of high school, and the white hat is a sign of that accomplishment.

They wear the white hat everywhere they go for the two or three weeks after final exams, and it awakens a deep sentimentality in the usually practical and private Danes. It has a sort of magic.

When my daughter received her white cap last year, total strangers stopped her in the street to say "Congratulations on the hat" – tillykke med huen. Bus drivers congratulated her as she boarded, and so did supermarket clerks at the checkout counter.

Getting the hat is seen as a very happy occasion on the road from childhood to the big wide world. The white cap holds a special place in the Danish national consciousness.

The open-backed truck tour

If you visit in Denmark in June, you'll see teenagers celebrating their graduation, riding through town on the back of open-backed trucks, wearing their fresh white caps and cheering or blowing whistles. Using there's some pop music pumping at a very high volume.

The sides of the truck are covered with white banners, traditionally bedsheets, on which are painted slogans that are more or less obscene.

Everybody on the truck except the driver is several beers in and shouting at passerby on the sidewalk, who shout back.