History Trivia - Saint Celestine V resigns the papacy after only five months

December 13

863 Boudouin with the Iron Arm, earl of Flanders, wed Charles II the Bald of France's daughter Judith. He was daring warrior who fell in love with the youthful widow of two English kings, married her and fled with his bride to Lorraine. Charles, though at first angry, was at last conciliated, and made his son-in-law margrave of Flanders, which he held as a hereditary fief. The Norsemen were continually devastating the coastlands at this time, and Baldwin was entrusted with this outlying borderland in order to defend it. He was the first of a line of strong rulers of Flanders, who early in the 10th century exchanged the title of margrave for that of count.

1294 Saint Celestine V resigned the papacy after only five months; Celestine, who founded the Celestine order, was the first pope to abdicate. He had accepted the position only because the papacy had been vacant for years and needed a leader. In his eighties when elected, the work proved too problematic, and he resigned. 

1545 Council of Trent began.  The council would pass legislation dealing with the doctrinal challenges of the Protestant Reformation.