|It says post no bills. It didn't say "Post No Theses"|
Background: On October 31, 1517, a priest of the Augustinian Order, Martin Luther, sent a letter to Albrect of Mainz protesting some corrupt and theologically unsupported practices. In it, he enclosed a copy of his disputation on indulgences, which came to be called the 95 Theses. Most scholars now reject the notion that the theses were nailed to the door of the church in Wittenburg, where Dr. Luther taught theology. It hardly matters, however. The stercus hit the fan and the western Christian Church blew up like a slow-motion grenade. Thus began (or at very least accelerated) a process known as the Reformation.
Today, lots of Protestant Christian churches celebrate Reformation Day on the closest Sunday before Halloween. The most puritanical of churches don't acknowledge Halloween, of course. It is all Hallows' Eve, the night before All Saints' Day, and they of course do not approve of the veneration of saints. Moreover, there is a strong association with witchcraft, which is patently unacceptable.
In the German states of Brandenburg, Mecklenburg, West Pomerania, Saxony, Saxony-Anhalt, and Thuringia, Reformation Day is a school holiday. If you're in Germany, have a good day off, kids. If you're elsewhere, Happy Halloween if you celebrate it, or Reformation Day if you don't.