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Terms and concepts used in Genealogy


Dual Dating
A system of dating used in England and British North America from 1582-1752 for dates falling between January 1 and March 25. This practice resulted from the transition from the old Julian calendar to the new Gregorian calendar, which went into effect in 1582, but was not officially adopted by the British and the American colonies until 1752. The new Gregorian calendar recognized January 1 as the first day of the year, while the old Julian calendar recognized March 25 as the first day. Dates between January 1 and March 25 prior to the calendar change in 1752 were often written with both year numbers separated by a slash as in 5 January 1712/13.


Gregorian Calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree or "papal bull" signed on 24 February 1582. Only four Catholic countries adopted the new calendar on the date specified by the bull. Other Catholic countries experienced some delay before adopting the reform; and non-Catholic countries, not being subject to the decrees of the Pope, initially rejected or simply ignored the reform altogether. Although most countries eventually adopted the Gregorian calendar, the adoption was sporadic. For example; Turkey officially continued to use the Julian calendar until 1926 when it finally transitioned to the Gregorian calendar.


Julian Calendar
The Julian calendar began in 45 BC (709 AUC) as a reform of the Roman calendar by Julius Caesar. It was chosen after consultation with the astronomer Sosigenes of Alexandria. Evidence indicates it was designed to approximate the tropical year. The original Julian calendar began its year on 1 January though the recognized first day of the year changed a number of times over the centuries to include, 29 August, 30 August, 1 September, 23 September, 25 December, 1 March and 25 March. The Julian calendar remained in use into the 20th century in some countries as a civil calendar, but has been replaced by the Gregorian calendar in nearly all countries. The Roman Catholic Church, the Eastern Rite Catholic Churches and Protestant churches have replaced the Julian calendar with the Gregorian calendar; however, the Orthodox Church (with the exception of Romania, Estonia and Finland) still use the Julian calendar for calculating the dates of moveable feasts. Some Orthodox churches have adopted the Revised Julian calendar for the observance of fixed feasts, while other Orthodox churches retain the Julian calendar for all purposes. The Julian calendar is still used by the Berber people of North Africa, and on Mount Athos.

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