May 23 - 1618 - The Second Defenestration of Prague
In 1618, Protestants in Bohemia inaugurated the Thirty Years' War by throwing two Catholic nobles out of a window. Not only did that really happen, it even has a fancy name--The Defenestration of Prague. And as it was the second time people had been thrown from a window in anger in Prague, it became known as The Second Defenestration of Prague. Remarkably, it's a massively important historical event.