@stimuloog The nearest Monday afterwards is a Public Holiday. Some places have May Day celebrations I think, but it's a fairly recent innovation. It's not one of the "traditional" public holiday. I'll report back if I find out more...
@stimuloog Further investigation reveals a variety of pagan, traditional and modern traditions all falling into a "May Day" celebration of some kind. The earlier traditions focus on the time of year (start of summer etc), the later traditions on International Workers Rights. In Roman Catholic tradition May is associated with the Virgin Mary, in Orthodox tradition May is the month the Apostle and Evangelist John died in Ephesus. In 1889 it was chosen to mark International Workers Rights by the socialists and communists of the Second International, noting the unrest in Chicago following workers' rights demonstrations a few years earlier. So, take your pick!