Walpurgisnacht, or Walpurgis' Night is not the vernal equinox (the vernal equinox, also Ostara, is around March 21st, when the sun is entering the
constellation Aries from earth's
perspective). Walpurgis' Night is the evening of April 31st, which leads to May 1st, and is around the time of the Celtic Beltane (From an astronomer or astrologer's
perspective, the sun will be around the 15th degree of Taurus from earth's
perspective, or simply the middle portion of Taurus. It is also the 2nd decan of Taurus). As a key note, Beltane is related to fertility rituals (after all, it is the spring) and may also be known as May Day.
The name "Walpurgis" is referring to St. Walburga, who was an educated English abess that studied Latin (remember, educated women were rare back then), and migrated to Heidenheim, Germany, and died there around 780 CE. May 1st is also the day of the removal of her bones from Heidenheim to Eichstädt.
The witchy connotations of Walpurgis' Night may have sprung up around the late 18th century and
early 19th century CE in Germany, and memorialized when Goethe published his play about the legend of Faust in 1808. It is possible that Walpurgis' Night may have been associated with witchcraft due to the pagan's religious practices around this time in accordance with May Day. Coupled with the church's demonization of pagan practices, these religious practices around this time was marked as witchcraft, hence leaving Walpurgis' Night with a witchy
association.
Walpurgisnacht, as seen in Puella Magi Madoka Magica, is one of
the many references in the anime to the
Germanic Faustian play by Johann
Wolfgang von Goethe, Goethe's Faust.
