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 calendar [Lat., from Kalends], system of reckoning time for the practical purpose of recording past events and calculating dates for future plans. The calendar is based on noting ordinary and easily observable natural events, the cycle of the sun through the seasons
..... Click the link for more information. , 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 Trent, Council of, 1545–47, 1551–52, 1562–63, 19th ecumenical council of the Roman Catholic Church, convoked to meet the crisis of the Protestant Reformation .
..... Click the link for more information. ) 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 Saint Bartholomew's Day, massacre of, murder of French Protestants, or Huguenots , that began in Paris on Aug. 24, 1572. It was preceded, on Aug. 22, by an attempt, ordered by Catherine de' Medici , on the life of the Huguenot leader Admiral Coligny .
..... Click the link for more information. , 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.

Gregory XIII

orig. Ugo Buoncompagni

(born June 7, 1502, Bologna, Romagna—died April 10, 1585, Rome, Papal States) Pope (1572–85) who promulgated the Gregorian calendar. After teaching at the University of Bologna, he served as a delegate to the Council of Trent, became a cardinal in 1565, and was elected pope in 1572. A promoter of the Counter-Reformation, he sought to execute the reform decrees of the council. He compiled the Index librorum prohibitorum and founded several colleges and seminaries, delegating their direction to the Jesuits. Aided by an astronomer and a mathematician, he corrected the errors in the Julian calendar and issued the Gregorian calendar (1582), which was later adopted worldwide.

Gregory XIII

1502--85, pope (1572--85). He promoted the Counter-Reformation and founded seminaries. His reformed (Gregorian) calendar was issued in 1582