Epoch
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.
The moment of epoch is usually decided by congruity, or by following conventions understood from the epoch in question. The epoch moment or date is usually defined from a specific, clear event of change, an epoch event. In a more gradual change, a deciding moment is chosen when the epoch criterion was reached.
Calendar eras
Pre-modern eras
- The Obatala, also regarded as the creation of the earth.
- Anno Mundi (years since the creation of the world) is used in the Byzantine calendar (5509 BC).
- Anno Mundi (years since the creation of the world) as used in the Hebrew calendar (3761 BC).[1][2]
- The Mesoamerican Long Count Calendaruses the creation of the fourth world in 3114 BC.
- Olympiads, the ancient Greek era of four-year periods between Olympic Games, beginning in 776 BC.
- Ab urbe condita ("from the foundation of the city"), used to some extent by Roman calendars of the Roman imperial period (753 BC).
- Buddha's parinirvana).
- The term Hindu calendar may refer to a number of traditional Indian calendars. A notable example of a Hindu epoch is the Vikram Samvat (58 BC),[3] also used in modern times as the national calendars of Nepal and Bangladesh.
- The date of birth of Jesus.) This epoch was applied retrospectively to the Julian calendar, long after its original creation by Julius Caesar.
- The epoch of the Hijra) or AH. This calendar is used in Sunni Islamand related sects.
- The epoch of the official Iranian calendar is also the Hijra, but it is a solar calendar; each year begins at the Northern spring equinox. This calendar is used in Shia Islam and related sects.
Modern eras
- The Bahá'í calendar is dated from the vernal equinox of the year the Báb proclaimed his religion (AD 1844). Years are grouped in Váḥids of 19 years, and Kull-i-Shay of 361 (19×19) years.[5]
- In Phibunsongkhram decided to count the years since 543 BC. This is the Thai solar calendarusing the Thai Buddhist Era. Except for this era, it is the Gregorian calendar.
- In the Ancien Regime).
- The Saka era(AD 78).
- The Xinhai Revolution, which overthrew the Qing Empire.
- Kim Il-Sung.
- The Mussolini's March on Rome in 1922, and was in use only in countries under hegemony of the Fascist regime of Benito Mussolini. It has been defunct since the fall of the Italian Social Republicin 1945.
- In the scientific Before Present system of numbering years for purposes of radiocarbon dating, the reference date is January 1, 1950 (though the specific date January 1 is quite unnecessary, as radiocarbon dating has limited precision).[6][7]
- Different branches of Freemasonry have selected different years to date their documents according to a Masonic era, such as the Anno Lucis (A.L.).
- The geological time scale.
Regnal eras
The official
Other applications
An epoch in computing is the time at which the representation is zero. For example, Unix time is represented as the number of seconds since 00:00:00 UTC on 1 January 1970, not counting leap seconds.
An epoch in astronomy is a reference time used for consistency in calculation of positions and orbits. A common astronomical epoch is J2000, which is noon on January 1, 2000, Terrestrial Time.
An epoch in Geochronology is a period of time, typically in the order of tens of millions of years. The current epoch is the Holocene.
See also
- Dating creation – Using creation myths to date the Earth
- Era – Span of time defined for the purposes of chronology or historiography
- Geologic time scale – System that relates geologic strata to time
- Lunisolar calendar – Calendar with lunar month, solar year
- Metonic cycle – 19-year pattern in lunisolar calendars
- Saros (astronomy) – Cycles used to predict eclipses of the Sun and Moon
- Timekeeping on Mars – Proposed approaches to tracking date and time on the planet Mars
References
- ^ Solomin, Rachel M. "Counting the Jewish Years". myjewishlearning.com. Archived from the original on 2020-02-12. Retrieved 2016-12-27.
- ^ Lee, Scott E. (2006). "Overview of Calendars". rosettacalendar.com. Archived from the original on 2020-08-20. Retrieved 2006-10-23.
- ISBN 978-0-521-70238-6.
- ^ Blackburn, B; Holford-Strevens, L (2003). "Incarnation era". The Oxford Companion to the Year: An exploration of calendar customs and time-reckoning. Oxford University Press. p. 881.
- ^ Richards, E. G. (2013). "Calendars". In Urban, S. E.; Seidelman, P. K. (eds.). Explanatory Supplement to the Astronomical Almanac (3rd ed.). Mill Valley, CA: University Science Books. pp. 616–617.
- ^ Higham, Thomas. "Radiocarbon dating – Age calculation". c14dating.com. Thomas Higham (archaeologist). Archived from the original on June 10, 2007. Retrieved December 31, 2009.
- from the original on August 17, 2020. Retrieved October 5, 2018.