Cross Quarter Day May 1 - May Day is closely connected to the evening before it - the "Walpurgisnacht" or May Eve. Its roots can be found in pre-Christian Frühjahrsfests. Walpurgisnacht is situated directly opposite Halloween and is the end marker in the seasonal cycle which begins with Candlemas/Groundhog Day. Children play pranks on unsuspecting victims around midnight on April 30, similar to Halloween, and some even dress up as witches and evil spirits. The Brocken, the highest peak in the Harz Mountains, is known as the mythical meeting place of the witches. Witches' fires may burn in some places. Since noise was deemed the most effective way to drive off evil spirits many ways of making noise are known. On May Day earth spirits like fairies and elves (the ancient dead) would come out of the hills and barrows to dance on May Eve and well into the summer.
References to Walpurgis[edit]
Anton Szandor LaVey chose Walpurgis Night in 1966 to found the Church of Satan.
Adolf Hitler, with several members of his staff (including Joseph Goebbels), committed suicide on Walpurgisnacht, April 30/May 1, 1945.
Gustav Meyrink wrote a novel called "Walpurgisnacht" in 1917, about a carnivalesque popular uprising in Prague against the city's longtime Germanic monarchs.
"War Pigs", a song by Black Sabbath, was originally titled "Walpurgis," and made reference to black masses and satanic rituals.
According to an interview with J.K. Rowling, the Death Eaters were originally called the Knights of Walpurgis, a pun on Walpurgis Night.
The Illuminatus! Trilogy by Robert Anton Wilson make repeated references to Walpurgisnacht.
all from Wikipedia:Walpurgis Night