Calendar era

In antiquity,

For over a thousand years, ancient Assyria used a system of eponyms to identify each year. Each year at the Akitu festival (celebrating the Mesopotamian new year), one of a small group of high officials (including the king in later periods) would be chosen by lot to serve as the limmu for the year, which meant that he would preside over the Akitu festival and the year would bear his name. The earliest attested limmu eponyms are from the Assyrian trading colony at Karum Kanesh in Anatolia, dating to the very beginning of the 2nd millennium BC,^[2] and they continued in use until the end of the Neo-Assyrian Period, c. 612 BC.

Assyrian scribes compiled limmu lists, including an unbroken sequence of almost 250 eponyms from the early 1st millennium BC. This is an invaluable chronological aid, because a solar eclipse was recorded as having taken place in the limmu of Bur-Sagale, governor of Guzana. Astronomers have identified this eclipse as one that took place on 15 June 763 BC, which has allowed absolute dates of 892 to 648 BC to be assigned to that sequence of eponyms.^[3] This list of absolute dates has allowed many of the events of the Neo-Assyrian Period to be dated to a specific year, avoiding the chronological debates that characterize earlier periods of Mesopotamian history.

Olympiad dating

Among the ancient Greek historians and scholars, a common method of indicating the passage of years was based on the Olympic Games, first held in 776 BC. The Olympic Games provided the various independent city-states with a mutually recognizable system of dates. Olympiad dating was not used in everyday life. This system was in use from the 3rd century BC. The modern Olympic Games (or Summer Olympic Games beginning 1896) do not continue the four year periods from ancient Greece: the 669th Olympiad would have begun in the summer of 1897, but the modern Olympics were first held in 1896.^[4]: 769

Indiction cycles

Another common system was the

The rule for computing the indiction from the AD year number, which he had just invented, was stated by Dionysius Exiguus: add 3 and divide by 15; the remainder is the indiction, with 0 understood to be the fifteenth indiction.^[4]: 770 Thus the indiction of 2001 was 9.^[5] The beginning of the year for the indiction varied.^{[4]: 769–71}

Seleucid era

The Seleucid era was used in much of the Middle East from the 4th century BC to the 6th century AD, and continued until the 10th century AD among Oriental Christians. The era is computed from the epoch 312 BC: in August of that year

The use of consular dating ended in AD 541 when the emperor Justinian I discontinued appointing consuls. The last consul nominated was Anicius Faustus Albinus Basilius. Soon afterwards, imperial regnal dating was adopted in its place.

Dating from the founding of Rome

Another method of dating was

Several epochs for this date were in use by

Historical Roman dating employed several different dates for the beginning of the year. Modern application of the AUC era generally ignores this, the known mistakes[6] in Varro's own calculations, and the 752 BC epoch used by the Fasti and later Secular Games, such that AD 2024 is generally considered equivalent to AUC 2777 (2024 + 753).

Regnal years of Roman emperors

Another system that is less commonly found than might be thought was the use of the

Some regions of the Roman Empire dated their calendars from the date of Roman conquest, or the establishment of Roman rule.

The Spanish era counted the years from 38 BC, probably the date of a new tax imposed by the Roman Republic on the subdued population of Iberia. The date marked the establishment of Roman rule in Spain and was used in official documents in Portugal, Aragon, Valencia, and in Castile, into the 14th century. This system of calibrating years fell to disuse in 1381 and was replaced by today's Anno Domini.^[9]

Throughout the Roman and Byzantine periods, the Decapolis and other Hellenized cities of Syria and Palestine used the Pompeian era, counting dates from the Roman general Pompey's conquest of the region in 63 BC.

Maya

A different form of calendar was used to track longer periods of time, and for the inscription of calendar dates (i.e., identifying when one event occurred in relation to others). This form, known as the Long Count, is based upon the number of elapsed days since a mythological starting-point. According to the calibration between the Long Count and Western calendars accepted by the great majority of Maya researchers (known as the GMT correlation), this starting-point is equivalent to 11 August, 3114 BC in the proleptic Gregorian calendar or 6 September in the Julian calendar (−3113 astronomical).

Other dating systems

A great many local systems or

Late Antiquity and Middle Ages

Most of the traditional calendar eras in use today were introduced at the time of transition from

• The
  Byzantine Calendar
  places Creation at the beginning of its year 1, namely 5509 BC. Its first known use occurred in the 7th century AD, although its precursors were developed about AD 400. The year 7509 of this era began in September 2000.
• The
  Era of Martyrs or Era of Diocletian is reckoned from the beginning of the reign of Roman Emperor Diocletian; the first year of this era was 284/5. It was not the custom to use regnal years in Rome, but it was the custom in Roman Egypt, which the emperor ruled through a prefect (the king of Egypt). The year number changed on the first day of the Egyptian month Thoth (29 August three years out of four, 30 August the year before a Roman leap year.) Diocletian abolished the special status of Egypt, which thereafter followed the normal Roman calendar: consular years beginning on 1 January. This era was used in the Easter tables prepared in Alexandria long after the abdication of Diocletian, even though Diocletian was a notorious persecutor of Christians. The Era of Diocletian was retained by the Coptic Church and used for general purposes, but by 643 the name had been changed to Era of the Martyrs.^[4]
  ^: 766–7
• The Incarnation Era is used by Ethiopia. Its epoch is 29 August, AD 8 in the Julian calendar.
• The Armenian calendar has its era fixed at AD 552.

• A.D. (or AD) – for the
  Anno Salutis, meaning "in the year of salvation" is identical. Originally intended to number years from the Incarnation of Jesus, according to modern thinking the calculation was a few years off. Years preceding AD 1 are numbered using the BC era, avoiding zero or negative numbers. AD was also used in the medieval Julian calendar, but the first day of the year was either 1 March, Easter, 25 March, 1 September, or 25 December, not 1 January. To distinguish between the Julian and Gregorian calendars, 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 and for years not beginning on 1 January. New Style
  (N.S.) was used for the Gregorian calendar and for Julian calendar years beginning on 1 January. Many countries switched to using 1 January as the start of the numbered year at the same time as they switched from the Julian calendar to the Gregorian calendar, but others switched earlier or later.
• B.C. (or BC) – meaning "Before Christ". Used for years before AD 1, counting backwards so the year n BC is n years before AD 1. Thus there is no year 0.
• C.E. (or CE) and B.C.E. (or BCE) – meaning "Common Era" and "Before the Common Era", numerically equivalent to AD and BC, respectively (in writing, "AD" precedes the year number, but "CE" follows the year: AD 1 = 1 CE.)^[10] The Latin equivalent vulgaris aera was used as early as 1615 by Johannes Kepler.^[11] The English abbreviations C.E. and B.C.E. were introduced in the 19th century by Jewish intellectuals, wishing to avoid the abbreviation for dominus "lord" in implicit reference to Christ.^[12] By the later 20th century, the abbreviations had come into wider usage by authors who wished to emphasize secularism.^[13]

Dionysian-derived

• Astronomical year numbering equates its year 0 with 1 BC, and counts negative years from 2 BC backward (−1 backward), so 100 BC is −99.
• The human era, also named Holocene era, proposed by Cesare Emiliani adds 10,000 to AD years, so that AD 1 would be the year 10,001.^[14]
• Anno Lucis of Freemasonry adds 4000 years to the AD year.

Islamic

• Hijra", Muhammad's emigration from Mecca to Medina in September 622, which occurred in its first year, used in the Islamic calendar. Since the Islamic calendar is a purely lunar calendar of about 354 or 355 days, its year count increases faster than that of solar and lunisolar calendars
  .
• Iranian calendar
  to denote the number of solar years since the Hijra. The year beginning at the vernal equinox equals the number of the Gregorian year beginning at the preceding 1 January minus 621.

• Hindu calendar, counting from the start of the Kali Yuga, with its epoch on 18 February, 3102 BC Julian (23 January, 3102 BC Gregorian), based on Aryabhata (6th century).
• Vikrama Samvat
  , 56-57 BC, introduced about the 12th century.
• S.E. or (SE) – for the Saka Era, used in some Hindu calendars and in the Indian national calendar
  , with an epoch near the vernal equinox of year 78 (its year 0); its usage spread to Southeast Asia before year 1000. This era is also used (together with the Gregorian calendar) in the Indian national calendar, the official civil calendar used in communiques issued by the Government of India.
• Lakshmana Era, established by the Bengali ruler Lakshmana Sena with an epoch of 1118–1119. It was used for at least 400 years in Bihar and Bengal.

Southeast Asia

The Hindu Saka Era influences the calendars of southeast Asian indianized kingdoms.

• Phibunsongkhram decided to count the years since 543 BC. This is the Thai solar calendar
  using the Thai Buddhist Era aligned to the western solar calendar.
• BE for Burmese Era – from
  Saka Era of the Indian national calendar

• Bahá'í calendar dates from the year of the declaration of the Báb
  . Years are counted in the Bahá'í Era (BE), which starts its year 1 from 21 March 1844.

• The
  Yazdegerd III of Persia, crowned 16 June 632, continued to be used as the reference year, abbreviated Y.Z.
  or "Yazdegerd era".

Political

• The Republican Era of the
  French Republican Calendar was dated from 22 September 1792, the day of the proclamation of the French First Republic
  . It was used in Revolutionary France from 24 October 1793 (on the Gregorian calendar) to 31 December 1805.
• The Positivist calendar of 1844 takes 1789 as its epoch.
• The
  Kim Il-Sung
  .
• The
  Common era
  was presented in Arabic numerals and the year of the fascist era in Roman numerals. The year of the Fascist calendar began on 29 October, so, for example, 27 October 1933 was XI E.F. but 30 October 1933 was XII E.F.
• China traditionally reckoned by the regnal year of its emperors, see Chinese era name. Most Chinese do not assign numbers to the years of the Chinese calendar, but the few who do, like expatriate Chinese, use a continuous count of years from the reign of the legendary Yellow Emperor, using 2698 BC as year 1. Western writers begin this count at either 2637 BC or 2697 BC (see Chinese calendar). Thus, the Chinese years 4637, 4697, or 4698 began in early 2000.
• In Korea, from 1952 until 1961 years were numbered via Dangi years, where 2333 BC was regarded as the first such year.
• The Assyrian calendar, introduced in the 1950s, has its era fixed at 4750 BC.
• The Japanese calendar dates from the accession of the current Emperor of Japan. The current emperor took the throne in May 2019, which became Reiwa 1, and which was until then Heisei 31.
• The
  Constitution is dated "the Seventeenth Day of September in the Year of our Lord one thousand seven hundred and Eighty seven and of the Independence of the United States of America the Twelfth."^[15] Presidential proclamations are also dated in this way.^[16]

• A.D. – "After Dianetics". In Scientology, years are numbered relative to the first publication of the book Dianetics: The Modern Science of Mental Health (1950).^[17]
• attention deficit disorder).^{[citation needed}
  ]
• e.v. – Era vulgaris. (From Latin, meaning "common era", usually stylized in lowercase.) Used by some followers of
  Thelemic calendar which is used by some Thelemites to designate a number of years since Crowley's inauguration of the so-called Aeon of Horus, which occurred on 20 March 1904, and coincides with both the Thelemic new year and a holiday known as the Equinox of the Gods. The abbreviation "A.N.", for Aerae Novae ("New Era" in Latin), is also used for dates in the Thelemic calendar.^{[citation needed}
  ]

• B.P. – for Before Present, specifically, the number of radiocarbon years before 1950.
• epoch
  . Today (noon-to-noon UTC) the value is 2460417.
• Unix epoch set at 00:00:00 or midnight UTC of 1 January 1970, though there are problems with Unix implementation of Coordinated Universal Time
  (UTC).
• Holocene calendar

See also

• Calendar reform
• Common Era
• Julian day
• List of calendars

References