Calendar era: Encyclopedia - Calendar era

Calendar era

A calendar era is the year numbering system used by a calendar. For example, the Gregorian calendar numbers its years in the Western Christian era (the Coptic and Ethiopic churches have their own Christian eras, see below). The instant, date, or year from which time is marked is called the epoch of the era. There are many different calendar eras. Some are listed below along with their abbreviations (if any).

• A.D. (or AD) — for the Latin Anno Domini, meaning in the year of our Lord. Years are counted from the beginning of the dominant or Western Christian Era. AD is used in the Gregorian calendar. Anno Salutis, meaning in the year of salvation, is sometimes used to indicate this era.
  • Note: AD was also used in the medieval Julian Calendar as well, but the calendars are not identical. To distinguish between them, O.S. and N.S. were often added to the date, especially during the 17th and 18th centuries, when both calendars were in common use. Old Style (O.S.) was used for the Julian calendar. New Style (N.S.) was used for the Gregorian calendar.
• A.C., B.C. (or BC) — for the Latin Ante Christum, and the English Before Christ, respectively. In all cases, years count backward from the year AD 1. Note that there is no year 0 in the Julian or Gregorian calendars, but there is in astronomical year numbering, as well as in the Hindu and Buddhist calendars.
• C.E. (or CE) — meaning Common Era, which is used with the Gregorian calendar and is equivalent to the Anno Domini era. This use is similar to that of the Vulgar Era in the past.
• B.C.E. (or BCE) — meaning Before the Common Era. Used with the Gregorian calendar and equivalent to B.C..
• A.U.C. (or AUC) — for the Latin Ab Urbe Condita, meaning from the founding of the city (of Rome). The first day of its year was Founder's Day (April 21), although most modern historians assume that it coincides with the modern historical year (January 1 to December 31). It was rarely used in the Roman calendar and in the early Julian calendar — naming the two consuls that held office in a particular year was dominant. Dionysius Exiguus implied, but did not explicitly state, that AD 1 was 754 AUC, so that the year 2006 is the same as the year 2759 AUC (2006 + 753).
• A.M. (or AM) — for the Latin Anno Mundi, meaning in the year of the world. This is used in the Hebrew calendar which counts years from the creation of the world, which is thought to have taken place in the year 3761 BC. AM was also used for all first millennium world eras of the early Christian chronographers. Related to this are the Anno Lucis of Freemasonry, which adds 4000 years to the AD date, and the Aetos Kosmou of the Byzantine Greek Calendar (in which the year 7514 begins in September 2005), both of which claim to date from Creation.
• A.M. (or AM), Era of Martyrs — from the Latin Anno Martyrum (in the year of the martyrs). Used in the Coptic calendar, and equivalent to the old Anno Diocletiani, it counts years from the reign of emperor Diocletian. Its epoch is 29 August 284 in the Julian calendar.
• A.H. (or AH) — for the Latinized Anno Hegirae, meaning in the year of the Hijra, Prophet Muhammad's migration from Mecca to Medina in September 622, which is taken to be the beginning of the Muslim era. This is used in the Islamic calendar. (Note that, since the Islamic calendar is a purely lunar calendar, its year count increases faster than that of solar and lunisolar calendars.)
  • This era is also used in the Iranian calendar, often written as A.H.S. (or AHS) to indicate the solar years since the Hijra.
• S.E. or (SE) — for the Saka Era, used in some Hindu calendars and the Indian national calendar, epoch dated from near the vernal equinox of year 78 (year 0); its usage spread to Southeast Asia before year 1000.
• B.E. — for the Buddhist Era, which has an epoch (origin) of 545 BC, but with an offset of one year from this zero year the difference BE − AD is 543 in Thailand.
• B.E. — for the Bahá'í Era beginning 21 March 1844. See Bahá'í calendar for more details.
• B.P. — for Before Present, specifically, the number of radiocarbon years before 1950, used in radiocarbon dating.
• The Incarnation Era is used by Ethiopia. Its epoch is 29 August 8 in the Julian calendar.
• The Republican Era of the French Republican Calendar was dated from 22 September 1792, the day of the proclamation of the French First Republic.
• The Seleucid Era, formerly used in much of the Middle East, uses the epoch 312 BC, the year when Seleucus I Nicator captured Babylon and began his reign over the Asian portions of Alexander the Great's empire.
• Chinese eras or Nian Hao were used sporadically from 156 BC and continuously from 140 BC. Until 1367 several were used during each emperor's reign. From 1368 until 1912 only one era name was used by each emperor, who was posthumously known by his era name.
  • The Republican era is used by the Republic of China (Taiwan) since 1929, and assigns year one to 1912, the first year of the republic. Coincidentally, this is the same as the Juche era used in North Korea.
  • Expatriate Chinese use a continuous count of years from the reign of the legendary Yellow Emperor, using the epoch 2698 BC (year 1). Western writers begin this count at either 2637 BC or 2697 BC (see Chinese calendar).
• Japanese eras or Nengo were used sporadically from 645 and continuously from 701. Until 1867 several were used during each emperor's reign. From 1868 only one era name has been used by each emperor. Since 1868, each emperor has been known posthumously by his era name.
• Korean eras or Dangi were used from 536 to 963 and from 1894 to 1910.

See also

• Julian Period
• Epoch (reference date)
• Epoch (other senses)

Categories: Calendars | Chronology | Historical eras

Adapted from the Wikipedia article "Calendar era", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki