Gregory XIII, 1502–85, pope (1572–85), an Italian named Ugo Buoncompagni, b. Bologna; successor of St. Pius V. He is best known for his work on the calendar, and the reformed calendar, the Gregorian, is named for him. He was prominent at the Council of Trent (1545, 1559–63; see Trent, Council of) and in the work of reform thereafter. He was created (1564) cardinal and later was legate to Spain. As pope, Gregory's absorbing interests were the education of the clergy and the conversion of Protestants. He especially patronized the Jesuits, whom he encouraged on their many missions, particularly in N Europe and in Japan. He proposed the deposition of Queen Elizabeth of England, and he advocated no compromise with German Protestants. He has been much criticized for a public thanksgiving at Rome for the massacre of Saint Bartholomew's Day, but he had been told that it was the suppression of a rebellion. He issued a new edition of the canon law. He was succeeded by Sixtus V.