May Day vs Vappu

As Easter was like Halloween, so my non Finnish friends may be unsure how Vappu is May Day.

They are on one and the same date, but are an amalgamation of different activities. May Day being associated with labour relations and Vappu being (of course) a pagan celebration...

Here's the history:
Vappu: From Helsingin Sanomat
The history of Vappu stems from Germany where May Eve is celebrated as Valpurgisnacht, a well-known witches' sabbath.
Walburga, the original Vappu, was born in around 710 AD, and she died 69 years later in Heidenheim, in what is now Germany. She was an abbess and a missionary. Her life was naturally a good one but what singled her out for canonisation was that after her death and the subsequent interment of her relics (on May 1, 870) in the Church of the Holy Cross in Eichstätt, strange things began to happen. Her shrine became an important pilgrimage site because of the clear liquid, referred to as a “miraculous oil”, that oozed from the rock on which her tomb was placed. Some twenty years after the interment, Walburga's relics were inspected and diffused, and this spread her cult status far and wide.
At this point we move into the realm of speculation. There are two possible theories. On the one side we have the possibility that soon after her death, the memory of her became confused with that of Waldborg, a pre-Christian fertility goddess, and the witches' sabbaths became known as Valpurgisnacht, without materially changing their contents. This confusion is not helped by the fact that Walburga is supposed to be a protectress of crops as well as a healer, and in art she is often pictured with three ears of corn in addition to her flask of medicinal oil.
The other scenario, which seems equally plausible, is that the abbess was seen as a handy tool for quietening down the witchcraft rituals associated with this time of the year. As so often throughout the history of the early Christian church, saints' days and other holy days were often placed strategically in the calendar to counter the effects of “less devout” pantheistic or pagan festivals, and this may be the case here, as St. Walburga and her healing oils were given the tough task of countering the bacchanalian orgies of April 30th.
This particular dodge might have worked for Christmas (timed to coincide with the very rowdy Saturnalia orgies of Roman days), but at least to judge by the standards of Finnish Vappu, there isn't very much of a devotional aspect to be seen.
What began in Scandinavia in the 18th century as a civilised at-home celebration amongst the academic set (many of whom had studied in Germany) has changed with time and was adopted here in Finland with the rise of nationalism amongst students in the mid-19th century.

The labour connection from Wikipedia
The holiday is most often associated with the commemoration of the social and economic achievements of the labor movement. The May 1st date is used because in 1884 the Federation of Organized Trades and Labor Unions demanded an eight-hour workday in the United States, to come in effect as of May 1, 1886. This resulted in the general strike and the U.S. Haymarket Riot of 1886, but eventually also in the official sanction of the eight-hour workday.