Pope Gregory XIII dies. Born Ugo Boncompagni, Gregory XIII is best known for commissioning a calendar that ends up being named after him: the Gregorian Calendar. That wasn't all there was to his pontificate, though.
Pope Gregory XIII played an important role at Council of Trent (1545, 1559-63) and was a vociferous critic of German Protestants. He even went so far as to hold a public thanksgiving at Rome for the Saint Bartholomew's Day Massacre.