Every day something happens that has never happened before. So you should be creating scenarios to anticipate the truly novel.
Things that happened on February 20 that had never happened before:
1258: Baghdad is sacked and the last Abbasid caliph of Baghdad, Al-Musta'sim, is executed by the forces of the invading Mongols led by Hulagu Khan, ending a succession that had lasted some five hundred years. Al-Musta'sim had done nothing to prepare a defense of Baghdad, having been told that the Mongols could be repelled easily by a force of the city's women throwing stones at them.
1935: Caroline Mikkelsen becomes the very first woman ever to set foot on the continent of Antarctica.
1943: A fissure opens up in the cornfield of Mexican farmer Dionisio Pulido. Within a few years, the entire surrounding area and several villages are buried and replaced by what is now the 1,391-foot cinder cone volcano Paricutin.
1962: John Glenn becomes the first American to orbit the earth.