Pope Gregory XIII (Latin: Gregorius XIII, Italian: Gregorio XIII, born Ugo Boncompagni; 7 January 1502 – 10 April 1585) was head of the Catholic Church and ruler of the Papal States from 13 May 1572 to his death in April 1585. He is best known for commissioning and being the namesake for the Gregorian calendar, which remains the internationally accepted civil calendar to this day.
Ugo Boncompagni was born the son of Cristoforo Boncompagni (10 July 1470 – 1546) and Angela Marescalchi, and paternal grandson of Giacomo Boncompagni and Camilla Piattesi, in Bologna, where he studied law and graduated in 1530. He later taught jurisprudence for some years, and his students included notable figures such as Cardinals Alexander Farnese, Reginald Pole and Charles Borromeo. He had an illegitimate son after an affair with Maddalena Fulchini, Giacomo Boncompagni, but before he took holy orders, making him the last Pope to have left issue.
At the age of 36, he was summoned to Rome by Pope Paul III (1534–1549), under whom he held successive appointments as first judge of the capital, abbreviator, and vice-chancellor of the Campagna e Marittima.
Pope Paul IV (1555–1559) attached him as datarius to the suite of Cardinal Carlo Carafa. Pope Pius IV (1559–1565) made him Cardinal-Priest of San Sisto Vecchio and sent him to the Council of Trent.
In the year 1552, Ugo Boncompagni confirmed the paternity of his son Giacomo (or Jacopo). As stated in the online Archivio Digitale Boncompagni Ludovisi: "One of the most valuable items to emerge from the new archival finds from the Villa Aurora is an autograph declaration in Latin and Italian dated 22 December 1552 by Ugo Boncompagni (1502–1585, from 1572 Pope Gregory XIII). Here, Ugo confirms his paternity of Giacomo (or Jacopo) Boncompagni (1548–1612) by Maddalena de' Fucchinis, a servant in the employ of his sister-in-law Laura Ferro. The future Pope explains in detail the circumstances of the boy's conception, which took place in 1547, in Bologna after the Council of Trent had moved to that city; his motive was to assure his inheritance rights following the death (in 1546) of his father Cristoforo Boncompagni."
He also served as a legate to Philip II of Spain (1556–1598), being sent by the Pope to investigate the Archbishop of Toledo Bartolomé Carranza. He formed a lasting and close relationship with the Spanish king, which aided his foreign policy aims as Pope.
After Pope Pius V (1566–1572) died, the conclave chose Cardinal Boncompagni, who assumed the name of Gregory XIII in homage to Gregory the Great, a 6th-century reforming pope. It was a very brief conclave, lasting less than 24 hours. Many historians have attributed this to the influence and backing of the Spanish king. Charles Borromeo and the cardinals, wishing reform, accepted Boncompagni's candidature and so supported him in the conclave, while the Spanish faction also deemed him acceptable due to his success as a nuncio in Spain.
Once in the chair of Saint Peter, Gregory XIII dedicated himself to reform of the Catholic Church. He implemented the recommendations of the Council of Trent. He mandated that cardinals reside in their sees without exception, and designated a committee to update the Index of Forbidden Books. Gregory XIII was also the patron of a new and greatly improved edition of the Corpus juris canonici. In a time of considerable centralisation of power, Gregory XIII abolished the Cardinals Consistories, replacing them with Colleges and appointing specific tasks for these colleges to work on. He was renowned for fierce independence; some confidants noted that he neither welcomed interventions nor sought advice. The power of the papacy increased under him, whereas the influence and power of the cardinals substantially decreased.
Gregory XIII also established the Discalced Carmelites, an offshoot of the Carmelite Order, as a distinct unit or "province" within the former by the decree "Pia consideratione" dated 22 June 1580, ending a period of great difficulty between them and enabling the former to become a significant religious order in the Catholic Church.
Formation of clergy and promotion of the arts and sciences
Gregory XIII was a generous patron of the Jesuit colleges in Rome. The Roman College of the Jesuits grew substantially under his patronage, and became the most important centre of learning in Europe for a time. It is now named the Pontifical Gregorian University. Pope Gregory XIII also founded numerous seminaries for training priests, beginning with the German College at Rome, and put them in the charge of the Jesuits.
In 1575, he gave official status to the Congregation of the Oratory, a community of priests without vows, dedicated to prayer and preaching (founded by Saint Philip Neri). In 1580, he commissioned artists, including Ignazio Danti, to complete works to decorate the Vatican and commissioned The Gallery of Maps.
Gregory also transformed the Dominican studium founded in the 13th century at Rome into the College of St. Thomas in 1580, as recommended by the Council of Trent. This college was the precursor of the Pontifical University of Saint Thomas Aquinas Angelicum.
Pope Gregory XIII is best known for commissioning the Gregorian calendar, initially authored by the physician/astronomer Aloysius Lilius and aided by Jesuit priest/astronomer Christopher Clavius, who made the final modifications. This calendar is more accurate than the Julian calendar, which treats each year as 365 days and 6 hours in length, even though the actual length of a year is slightly less (365 days, 5 hours, and 49 minutes). As a result, the date of the vernal equinox had slowly, over the course of 13 centuries, slipped to 10 March, while the computus (calculation) of the date of Easter still followed the traditional date of 21 March. Clavius verified this phenomenon.
Gregory subsequently decreed, by the papal bull Inter gravissimas of 24 February 1582, that the day after Thursday, 4 October 1582 would be the fifteenth, not the fifth, of October. The new calendar replaced the Julian calendar, which had been used since 45 BC. Because of Gregory's involvement, the new calendar came to be known as the Gregorian calendar and has been almost universally adopted.
Much of the populace bitterly opposed this reform; they feared it was an attempt by landlords to cheat them out of a week and a half's rent. However, the Catholic countries of Spain, Portugal, Poland-Lithuania, and the Italian states complied. France, some states of the Dutch Republic and various Catholic states in the Holy Roman Empire and Switzerland (both countries were religiously split) followed suit within a year or two. Austria and Hungary followed in 1587.
However, more than a century passed before Protestant Europe accepted the new calendar. Denmark-Norway, the remaining states of the Dutch Republic, and the Protestant states of the Holy Roman Empire and Switzerland adopted the Gregorian reform in 1700–01. By that time, the calendar trailed the seasons by 11 days. Great Britain, its American colonies and Ireland adopted the reformed calendar in 1752, where Wednesday 2 September 1752 was immediately followed by Thursday 14 September 1752; they were joined by the last Protestant holdout, Sweden, on 1 March 1753.
The Gregorian calendar was not accepted in eastern Christendom for several hundred years, and then only as the civil calendar.