Some of these days derive from politics, and some from Roman Catholic traditions that predate the current national church.
Some are simply the Scandinavian tradition of starting the celebrations of a special day on the evening before the actual day.
The day is also known as Arbejdernes kamp og festdag (Workers day of struggle and celebration) referring to the celebration of the past victories of the workers movement, especially the 8-hours working day.
Many, both families and young people, meet at the sites of the political meetings holding picnics and drink beer and other alcoholic beverages.
Copenhagen's Fælledparken is well known for its annual May 1 celebrations, gathering an average of a hundred thousand people at the meeting of the central Labour Union "LO".