Question: Which title is used for leader of the institution which thought the seasonal drift in the date of Easter was unacceptable?

full_context: Document 1: St. Peter's Basilica: The Papal Basilica of St. Peter in the Vatican (Italian: Basilica Papale di San Pietro in Vaticano), or simply St. Peter's Basilica (Latin: Basilica Sancti Petri), is an Italian Renaissance church in Vatican City, the papal enclave within the city of Rome.
Document 2: Catholic Church in the United States: The Catholic Church in the United States is part of the worldwide Catholic Church in communion with the Pope in Rome. With 70.4 million members, it is the largest religious denomination in the United States, comprising 22% of the population as of 2017. The United States has the fourth largest Catholic population in the world after Brazil, Mexico and the Philippines, the largest Catholic minority population, and the largest English - speaking Catholic population. The central leadership body of the Catholic Church in the United States is the U.S. Conference of Catholic Bishops.
Document 3: Gregorian calendar: The Council of Trent approved a plan in 1563 for correcting the calendrical errors, requiring that the date of the vernal equinox be restored to that which it held at the time of the First Council of Nicaea in 325 and that an alteration to the calendar be designed to prevent future drift. This would allow for a more consistent and accurate scheduling of the feast of Easter. In 1577, a Compendium was sent to expert mathematicians outside the reform commission for comments. Some of these experts, including Giambattista Benedetti and Giuseppe Moleto, believed Easter should be computed from the true motions of the sun and moon, rather than using a tabular method, but these recommendations were not adopted. The reform adopted was a modification of a proposal made by the Calabrian doctor Aloysius Lilius (or Lilio).
Document 4: Gregorian calendar: The Gregorian calendar was a reform of the Julian calendar instituted in 1582 by Pope Gregory XIII, after whom the calendar was named, by papal bull Inter gravissimas dated 24 February 1582. The motivation for the adjustment was to bring the date for the celebration of Easter to the time of year in which it was celebrated when it was introduced by the early Church. Although a recommendation of the First Council of Nicaea in 325 specified that all Christians should celebrate Easter on the same day, it took almost five centuries before virtually all Christians achieved that objective by adopting the rules of the Church of Alexandria (see Easter for the issues which arose).
Document 5: Vatican City: Vatican City (/ ˈvætɪkən ˈsɪti / (listen); Italian: Città del Vaticano (tʃitˈta ddel vatiˈkaːno); Latin: Civitas Vaticana), officially Vatican City State or the State of Vatican City (Italian: Stato della Città del Vaticano; Latin: Status Civitatis Vaticanae), is a country located within the city of Rome. With an area of approximately 44 hectares (110 acres), and a population of 1,000, it is the smallest state in the world by both area and population. However, formally it is not sovereign, with sovereignty being held by the Holy See.
Document 6: Catholic Church: The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with more than 1.299 billion members worldwide. As one of the oldest religious institutions in the world, it has played a prominent role in the history and development of Western civilisation. The church is headed by the Bishop of Rome, who is known as the Pope. The church's doctrines are summarised in the Nicene Creed. Its central administration, the Holy See, is in the Vatican City, an enclave within Rome, Italy.
Document 7: Christian: As of the early 21st century, Christianity has approximately 2.4 billion adherents. The faith represents about a third of the world's population and is the largest religion in the world. Christians have composed about 33 percent of the world's population for around 100 years. The largest Christian denomination is the Roman Catholic Church, with 1.17 billion adherents, representing half of all Christians.
Document 8: Pope Francis: Pope Francis (Latin: Franciscus; Italian: Francesco; Spanish: Francisco; born Jorge Mario Bergoglio; 17 December 1936) is the 266th and current Pope and sovereign of the Vatican City State. Francis is the first Jesuit pope, the first from the Americas, the first from the Southern Hemisphere, and the first pope from outside Europe since the Syrian Gregory III, who reigned in the 8th century.
Document 9: Gregorian calendar: The Gregorian calendar is a solar calendar. A regular Gregorian year consists of 365 days, but as in the Julian calendar, in a leap year, a leap day is added to February. In the Julian calendar a leap year occurs every 4 years, but the Gregorian calendar omits 3 leap days every 400 years. In the Julian calendar, this leap day was inserted by doubling 24 February, and the Gregorian reform did not change the date of the leap day. In the modern period, it has become customary to number the days from the beginning of the month, and February 29th is often considered as the leap day. Some churches, notably the Roman Catholic Church, delay February festivals after the 23rd by one day in leap years.
Document 10: Christmas: Although the month and date of Jesus' birth are unknown, by the early - to - mid fourth century the Western Christian Church had placed Christmas on December 25, a date that was later adopted in the East. Today, most Christians celebrate on December 25 in the Gregorian calendar, which has been adopted almost universally in the civil calendars used in countries throughout the world. However, some Eastern Christian Churches celebrate Christmas on December 25 of the older Julian calendar, which currently corresponds to January 7 in the Gregorian calendar, the day after the Western Christian Church celebrates the Epiphany. This is not a disagreement over the date of Christmas as such, but rather a preference of which calendar should be used to determine the day that is December 25. Moreover, for Christians, the belief that God came into the world in the form of man to atone for the sins of humanity, rather than the exact birth date, is considered to be the primary purpose in celebrating Christmas.
Document 11: Catholic Church in Ireland: Catholic Church in Ireland Eaglais Chaitliceach na hÉireann St Patrick's Cathedral, Armagh. Type National polity Orientation Catholic Church Governance Episcopal Pope Pope Francis Primate of All Ireland Eamon Martin Apostolic Nuncio Jude Thaddeus Okolo Region Island of Ireland Language English, Irish, Latin Headquarters Ara Coeli, Armagh, Northern Ireland Founder St. Patrick, by tradition. Origin Claims continuity with Celtic Christianity c. 430. Roman diocesan structure introduced c. 1111 at Synod of Ráth Breasail. Separations Church of Ireland (1536 / 1871) Members 3,729,000 (2016) Official website Irish Bishops' Conference
Document 12: Gregorian calendar: The Gregorian reform contained two parts: a reform of the Julian calendar as used prior to Pope Gregory XIII's time and a reform of the lunar cycle used by the Church, with the Julian calendar, to calculate the date of Easter. The reform was a modification of a proposal made by Aloysius Lilius. His proposal included reducing the number of leap years in four centuries from 100 to 97, by making 3 out of 4 centurial years common instead of leap years. Lilius also produced an original and practical scheme for adjusting the epacts of the moon when calculating the annual date of Easter, solving a long-standing obstacle to calendar reform.
Document 13: Gregorian calendar: Because the spring equinox was tied to the date of Easter, the Roman Catholic Church considered the seasonal drift in the date of Easter undesirable. The Church of Alexandria celebrated Easter on the Sunday after the 14th day of the moon (computed using the Metonic cycle) that falls on or after the vernal equinox, which they placed on 21 March. However, the Church of Rome still regarded 25 March as the equinox (until 342) and used a different cycle to compute the day of the moon. In the Alexandrian system, since the 14th day of the Easter moon could fall at earliest on 21 March its first day could fall no earlier than 8 March and no later than 5 April. This meant that Easter varied between 22 March and 25 April. In Rome, Easter was not allowed to fall later than 21 April, that being the day of the Parilia or birthday of Rome and a pagan festival.The first day of the Easter moon could fall no earlier than 5 March and no later than 2 April.
Document 14: Computus: Computus (Latin for ``computation '') is a calculation that determines the calendar date of Easter. Because the date is based on a calendar - dependent equinox rather than the astronomical one, there are differences between calculations done according to the Julian calendar and the modern Gregorian calendar. The name has been used for this procedure since the early Middle Ages, as it was considered the most important computation of the age.
Document 15: Holy See: The Holy See (Italian: Santa Sede; Latin: Sancta Sedes; Ecclesiastical Latin: (ˈsaŋkta ˈsedes)), also called the See of Rome, is the ecclesiastical jurisdiction of the Catholic Church in Rome, the episcopal see of the Pope, and an independent sovereign entity. It serves as the central point of reference for the Catholic Church everywhere and the focal point of communion due to its position as the pre-eminent episcopal see of the universal church. Today, it is responsible for the governance of all Catholics, organised in their Particular Churches, Patriarchates and religious institutes.
ground_truth: the Bishop of Rome, who is known as the Pope
sub_queries: Who thought that the seasonal drift in the date of Easter unacceptable? Answer: Roman Catholic Church
which title is used for the leader of Roman Catholic Church Answer: the Bishop of Rome, who is known as the Pope