In the fields of chronology Chronology is the science of arranging events in their order of occurrence in time, such as the use of a timeline. It is also "the determination of the actual temporal sequence of past events" and periodization Periodization is the attempt to categorize or divide time into named blocks. The result is a descriptive abstraction that provides a useful handle on periods of time with relatively stable characteristics. However, determining the precise beginning and ending to any "period" is often a matter of debate, an epoch means an instant in time chosen as the origin of a particular era An era is a commonly used word for long period of time. When used in science, for example geology, eras denote clearly defined periods of time of arbitrary but well defined length, such as for example the Mesozoic era from 252 Ma–66 Ma, delimited by a start event and an end event. When used in social history, eras may for example denote a period. The "epoch" then serves as a reference point from which time is measured. Time measurement units Time has been defined as the continuum in which events occur in succession from the past to the present and on to the future. Time has also been defined as a one-dimensional quantity used to sequence events, to quantify the durations of events and the intervals between them, and to quantify and measure the motions of objects and other changes are counted from the epoch so that the date and time of events can be specified unambiguously.
Events taking place before the epoch can be dated by counting negatively from the epoch, though in pragmatic periodization Periodization is the attempt to categorize or divide time into named blocks. The result is a descriptive abstraction that provides a useful handle on periods of time with relatively stable characteristics. However, determining the precise beginning and ending to any "period" is often a matter of debate practice, epochs are defined for the past, and another epoch is used to start the next era, therefore serving as the ending of the older preceding era. The whole purpose and criteria of such definitions is to clarify and co-ordinate scholarship about a period, at times, across disciplines.
Epochs are generally chosen to be convenient or significant by a consensus of the time scale's initial users, or by authoritarian fiat. The epoch moment or date is usually defined by a specific clear event, condition, or criteria— the epoch event or epoch criteria —from which the period or era or age is usually characterized or described.
Examples:
- by events:
- The assassination of the Roman Emperor The Roman Emperor was the ruler of the Roman State during the imperial period . The Romans had no single term for the office: Latin titles such as imperator (from which English emperor ultimately derives), augustus, caesar and princeps were all associated with it. In practice, the emperor was supreme ruler of Rome and supreme commander of the Alexander Severus Marcus Aurelius Severus Alexander , commonly called Alexander Severus, was the last Roman emperor (11 March 222–235) of the Severan dynasty. Alexander Severus succeeded his cousin, Elagabalus upon the latter's assassination in 222 AD, and was ultimately assassinated himself, marking the epoch event for the Crisis of the Third Century—nearly triggering the Crisis of the Third Century The Crisis of the Third Century (235–284 AD) was a period in which the Roman Empire nearly collapsed under the combined pressures of invasion, civil war, plague, and economic depression. The Crisis began with the assassination of Emperor Alexander Severus at the hands of his own troops, initiating a fifty-year period in which 20–25 claimants
- The defenestration of Prague The Defenestrations of Prague were two incidents in the history of Bohemia. The first occurred in 1419 and the second in 1618, although the term "Defenestration of Prague" is more commonly used to refer to the second incident. Both helped to trigger prolonged conflict within Bohemia and beyond. Defenestration is the act of throwing triggering the Thirty Years' War Pilsen – Lomnice – Sablat – Wisternitz – Humenné – White Mountain – Neu Titschein – Mingolsheim – Wimpfen – Höchst – Fleurus – Stadtlohn – Breda – Cádiz – Dessau Bridge – Lutter am Barenberge – Stralsund – Wolgast – St. Kitts– Swedish landing – Frankfurt – Magdeburg – Werben – 1st Breitenfeld –
- Queen Victoria Victoria was the Queen regnant of the United Kingdom of Great Britain and Ireland from 20 June 1837, and the first Empress of India of the British Raj from 1 May 1876, until her death. Her reign as the Queen lasted 63 years and 7 months, longer than that of any other British monarch before or since, and her reign is the longest of any female ascending to the throne giving the start of the Victorian era The Victorian era of the United Kingdom was the period of Queen Victoria's reign from June 1837 until her death on the 22nd of January 1901. The reign was a long period of prosperity for the British people, as profits gained from the overseas British Empire, as well as from industrial improvements at home, allowed an educated middle class to
- by criteria:
- The spurt in exploration, mercantilism, and colonization in the Age of Discovery The Age of Discovery, also known as the Age of Exploration, was a period in history starting in the 15th century and continuing into the early 17th century, during which Europeans and their descendants intensively explored and mapped the world. Historians often refer to the 'Age of Discovery' as the period of Portuguese and Spanish pioneer oceanic
- Particular ratios of animal fossils in a rock strata —various Geology epochs
Contents |
Calendars
Each 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 instant, date, or year from which time is marked is called the epoch of the era. There are many different calendar eras starts from an arbitrary epoch, which is often chosen to commemorate an important historical or mythological event. For example, the epoch of the anno Domini Anno Domini and Before Christ (abbreviated as BC or B.C.) are designations used to label years in the Julian and Gregorian calendars. The calendar era to which they refer is based on the traditionally reckoned year of the conception or birth of Jesus, with AD denoting years after the start of this epoch, and BC denoting years before the start of calendar era (the civil calendar era used internationally and in many countries) is the traditionally-reckoned Incarnation The Incarnation is the belief in Christianity that the second person in the Christian Godhead, also known as the Son or the Logos , "became flesh" when he was miraculously conceived in the womb of the Virgin Mary. The word Incarnate derives from Latin (in=in or into, caro, carnis=flesh) meaning "to make into flesh" or "to of Jesus Jesus of Nazareth , also known as Jesus Christ or simply Jesus, is the central figure of Christianity, which views him as the Messiah foretold in the Old Testament. Christians believe that Jesus is the Son of God (in the concept of the Trinity, he is God [as] the Son), who came to provide humankind with salvation and reconciliation with God by his.[1] Many other current and historical calendar eras Common Era, abbreviated as CE, is one of the designations for the world's most commonly used year-numbering system. The numbering of years using Common Era notation is identical to the numbering used with Anno Domini notation, 2010 being the current year in both notations and neither using a year zero. Common Era is also known as Christian Era and exist, each with its own epoch.
Asian national eras
- The official Japanese system The Japanese era calendar scheme is a common calendar scheme used in Japan, which identifies a year by the combination of the Japanese era name and the year number within the era. For example, the year 2010 is Heisei 22. As elsewhere in East Asia, the use of nengō, also known as "gengō" (元号?), was originally derived from Chinese numbers years from the accession of the current emperor The Emperor of Japan is the symbol of the state and of the unity of the Japanese people. He is the head of the Japanese Imperial Family. He is also the highest authority of the Shinto religion. Under Japan's present constitution, the Emperor is the "symbol of the state and the unity of the people," and is a ceremonial figurehead in a, regarding the calendar year during which the accession occurred as the first year.
- A similar system A Chinese era name is the era name, reign period, or regnal title used when traditionally numbering years in an emperor's reign and naming certain Chinese rulers (see the conventions). Some emperors have several era names, one after another, where each beginning of a new era resets the numbering of the year back to year one or yuán (元). The existed in China China is seen variously as an ancient civilization extending over a large area in East Asia, a nation and/or a multinational entity before 1912, being based on the accession year of the emperor (1911 was thus the fourth year of the Xuantong period). With the establishment of the Republic of China The Republic of China , commonly known as Taiwan, is a state in East Asia comprising the islands of Taiwan, Penghu, Kinmen, Matsu and other minor islands located off the east coast of mainland China. Neighbouring states include the People's Republic of China (PRC) to the west, Japan to the northeast, and the Philippines to the south in 1912, the republican era was introduced. It is still very common in Taiwan Taiwan, also known as Formosa , is an island situated in East Asia in the Western Pacific Ocean and located off the southeastern coast of mainland China. It has comprised most (99%) of the territory of the Republic of China (ROC) since the 1950s. The term "Taiwan" has also become a commonly used alternative name both domestically and to date events via the republican era. The People's Republic of China adopted the common era calendar in 1949 (the 38th year of the Chinese Republic).
- In India Home to the ancient Indus Valley Civilisation and a region of historic trade routes and vast empires, the Indian subcontinent was identified with its commercial and cultural wealth for much of its long history. Four major religions, Hinduism, Buddhism, Jainism and Sikhism originated here, while Zoroastrianism, Judaism, Christianity and Islam, the Indian national calendar The Indian national calendar is the official civil calendar in use in India. It is used, alongside the Gregorian calendar, by The Gazette of India, news broadcasts by All India Radio, and calendars and communications issued by the Government of India follows the Saka era The Shalivahana era, also known as the Saka era, is used with Hindu calendars, the Indian national calendar, and the Cambodian Buddhist calendar. Its year zero begins near the vernal equinox of the year 78.[citation needed]
- North Korea North Korea, officially the Democratic People's Republic of Korea (Chosongul: 조선민주주의인민공화국), is a country in East Asia, occupying the northern half of the Korean Peninsula. Its capital and largest city is Pyongyang. The Korean Demilitarized Zone serves as the buffer zone between North Korea and South Korea. The Amnok River and uses a system that starts in 1912 (= Juche The Juche Idea is the official state ideology of North Korea. It teaches that "man is the master of everything and decides everything," and that the Korean people are the masters of Korea's revolution. Juche is a component of Kimilsungism, North Korea's political system. The word literally means "main body" or "subject& 1), the year of the birth of their founder Kim Il-Sung Kim Il-sung was a Korean communist, and later Juche, politician who led North Korea from its founding in 1948 until his death. He held the posts of Prime Minister from 1948 to 1972 and President from 1972 to his death. He was also the General Secretary of the Workers Party of Korea. The year 2009 is "Juche 98". Juche means "autarky Autarky is the quality of being self-sufficient. Usually the term is applied to political states or their economic policies. Autarky exists whenever an entity can survive or continue its activities without external assistance. Autarky is not necessarily economic. For example, a military autarky would be a state that could defend itself without, self-reliance".
- In Thailand Thailand (pronounced /ˈtaɪlænd/ TYE-land or /ˈtaɪlənd/; Thai: ราชอาณาจักรไทย Ratcha Anachak Thai, IPA: [râːtɕʰa ʔaːnaːtɕɑ̀k tʰɑj]) (formerly Siam Thai: สยาม) is an independent country that lies in the heart of Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos in 1888 King Chulalongkorn Phra Bat Somdet Phra Poramintharamaha Chulalongkorn Phra Chunla Chom Klao Chao Yu Hua , or Rama V (20 September 1853 – 23 October 1910) was the fifth monarch of Siam under the House of Chakri. He was known to the Siamese of his time as Phra Phuttha Chao Luang (พระพุทธเจ้าหลวง - The Royal Buddha). He is considered decreed a National Thai Era dating from the founding of Bangkok Bangkok is the capital, largest urban area and primary city of Thailand. Known in Thai as Krung Thep Maha Nakhon (Thai: กรุงเทพมหานคร, pronounced [krūŋ tʰêːp máhǎː nákʰɔ̄ːn]), or กรุงเทพฯ Krung Thep ( [listen]) (help·info), meaning "city of angels" for short, it was a small trading on April 6, 1782. In 1912, New Year's Day was shifted to April 1. In 1941, Prime Minister Phibunsongkhram decided to count the years since 543 BC. This is the Thai solar calendar The Thai solar calendar, Suriyakati was adopted by King Chulalongkorn (Rama V) in 1888 as the Siamese version of the Gregorian calendar. It is the official calendar in Thailand, though Thai lunar calendar dates continue in use. Years are counted in the Buddhist Era (póota sàk-gà-râat พุทธศักราช พ.ศ.) that is 543 years using the Thai Buddhist Era. Except for this era, it is the Gregorian calendar.
Religious eras
- In Israel Israel , officially the State of Israel (Hebrew: מְדִינַת יִשְׂרָאֵל (help·info), Medīnat Yisrā'el; Arabic: دَوْلَةُ إِسْرَائِيلَ, Dawlat Isrā'īl), is a parliamentary republic in the Middle East located on the eastern shore of the Mediterranean Sea. It borders Lebanon in the north, Syria in the, the traditional Hebrew calendar The Hebrew calendar or Jewish calendar is a lunisolar calendar used by Jews. Today, the calendar is used predominantly for Jewish religious observances. It is used to determine the dates for Jewish holidays, and also to determine appropriate public reading of Torah portions, yahrzeits (dates to commemorate the death of a relative), and daily Psalm, using an era dating from Creation Anno Mundi abbreviated as AM or A.M., refers to a Calendar era counting from the Biblical creation of the world, is the official calendar. However, the Gregorian calendar is the de facto calendar and is commonly used. Government documents usually display a dual date. The beginning of year 1 of the Hebrew calendar occurred in the autumn of 3761 BC. Therefore, "Rosh Hashanah, the Jewish New Year, in September 2003 marked the transition from 5763 to 5764".[2][3]
- In the Islamic Islam (Arabic: الإسلام al-’islām, pronounced [ʔislæːm] [note 1]) is a strictly monotheistic religion articulated by the Qur’an, a text considered by its adherents to be the verbatim word of God (Arabic: الله, Allāh), and by the Prophet of Islam Muhammad's teachings and normative example (which is called the Sunnah in world, traditional Islamic dating The Islamic calendar or Muslim calendar or Hijri calendar is a lunar calendar based on 12 lunar months in a year of 354 or 355 days. It is the official calendar in Saudi Arabia and it's used to date events in many Muslim countries (concurrently with the Gregorian calendar), and used by Muslims everywhere to determine the proper day on which to according to the Anno Hegiræ (in the year of the hijra The Hijra is the migration of the Islamic prophet Muhammad and his followers to the city of Medina in 622 (Common Era). Alternate spellings of this Arabic word in the Latin alphabet are Hijrah, or Hegira in Latin) or AH era remains in use to a varying extent, especially for religious purposes. The official Iranian calendar The Iranian calendars or Persian calendars can refer to any in a succession of a set of calendars invented or used for over two millennia in Greater Iran. One of the longest chronological records in human history, the Iranian calendar has been modified time and again during its history to suit administrative, climatic, and religious purposes (used in Afghanistan The Islamic Republic of Afghanistan is a landlocked country in south-central Asia. It is bordered by Pakistan in the south and east, Iran in the west, Turkmenistan, Uzbekistan and Tajikistan in the north, and China in the far northeast. In addition; India claims a border with Afghanistan at the eastern Wakhan corridor as part of its claim on the as well as Iran Iran (Persian: ایران [ʔiˈɾɒn] ), officially the Islamic Republic of Iran is a country in Central Eurasia and Western Asia. The name Iran has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was also known to the western world as Persia. Both Persia and Iran are used) also dates from the hijra, but as it is a solar calendar A solar calendar is a calendar whose dates indicate the position of the earth on its revolution around the sun its year numbering does not coincide with the religious calendar.
- In Hinduism Hinduism is the predominant and indigenous religious tradition of the Indian subcontinent. Hinduism is often referred to as Sanātana Dharma by its adherents. Generic "types" of Hinduism that attempt to accommodate a variety of complex views span folk and Vedic Hinduism to bhakti tradition, as in Vaishnavism. Hinduism also includes yogic, all festival are according to the Hindu calendar The Hindu calendar used in ancient times has undergone many changes in the process of regionalization, and today there are several regional Indian calendars, as well as an Indian national calendar, based on the Vikram Samvat, which also functions as the national calendar of Nepal Nepal (pronounced /nəˈpal/ nə-PAHL, /-pal/ -PAWL; Nepali: नेपाल [neˈpal] ), officially the Federal Democratic Republic of Nepal, is a landlocked country in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India. With an area of 1 and Bangladesh Bangladesh (Bengali: বাংলাদেশ, pronounced /bæŋgləˈdɛʃ/; Bangladesh), officially the People's Republic of Bangladesh (Bengali: গণপ্রজাতন্ত্রী বাংলাদেশ Gônoprojatontri Banglādeśh) is a country in "South Asia." It is bordered by India on all sides except for a small.
Other
- In the French Republican Calendar The French Republican Calendar or French Revolutionary Calendar was a calendar proposed during the French Revolution, and used by the French government for about 12 years from late 1793 to 1805, and for 18 days in 1871 in Paris, a calendar used by the French government for about twelve years from late 1793, the epoch was the beginning of the "Republican Era", September 22, 1792 (the day the French First Republic was proclaimed, one day after the Convention abolished the monarchy).
- In the scientific Before Present system of numbering years for purposes of radiocarbon dating, the reference date is January 1, 1950 (though the use of January 1 is quite irrelevant, as radiocarbon dating has limited precision) [4][5].
- Different branches of Freemasonry have selected different years to date their documents according to a Masonic era, such has the Anno Lucis (A.L.).
Astronomy
Main article: Epoch (astronomy)In astronomy, an epoch is a specific moment in time for which celestial coordinates or orbital elements are specified, and from which other orbital parametrics are thereafter calculated in order to predict future position. The applied tools of the mathematics disciplines of Celestial mechanics or its subfield Orbital mechanics (both predict orbital paths and positions) about a center of gravity are used to generate an ephemeris (plural: ephemerides; from the Greek word ephemeros = daily) which is a table of values that gives the positions of astronomical objects in the sky at a given time or times, or a formula to calculate such given the proper time offset from the epoch. Such calculations generally result in an elliptical path on a plane defined by some point on the orbit, and the two focii of the ellipse. Viewing from another orbiting body, following its own trace and orbit, creates shifts in three dimensions in the spherical trigonometry used to calculate relative positions. Interestingly, these dynamics in three dimensions are also elliptical, which means the ephemeris need only specify one set of equations to be a useful predictive tool to predict future location of the object of interest.
Over time, inexactitudes and other errors accumulate, creating more and greater errors of prediction, so ephemeris factors need recalculated from time to time, and that requires a new epoch to be defined. Different astronomers or groups of astronomers used to define epochs to suit themselves, but these days of speedy communications, the epochs are generally defined in an international agreement, so astronomers world wide can collaborate more effectively. It was inefficient and error prone for data observed by one group to need translation (mathematic transformation) so other groups could compare information.
J2000.0
The current standard epoch is called "J2000.0" (Julian 2000, based on the Julian Calendar) and is approximately noon January 1, 2000 at the Royal Observatory, Greenwich, in London England:
- The Julian date 2451545.0 TT (Terrestrial Time).[6]
- This is equivalent to January 1, 2000, 11:59:27.816 TAI (International Atomic Time).[7] or
- January 1, 2000, 11:58:55.816 UTC (Coordinated Universal Time).
Computing
The time kept internally by a computer system is usually expressed as the number of time units that have elapsed since a specified epoch, which is nearly always specified as midnight Universal Time on some particular date.
Software timekeeping systems vary widely in the granularity of their time units; some systems may use time units as large as a day, while others may use nanoseconds. For example, for an epoch date of midnight UTC on January 1, 1900, and a time unit of a second, the time of midnight UTC on January 2, 1900 is represented by the number 86400, the number of seconds in one day. When times prior to the epoch need to be represented, it is common to use the same system, but with negative numbers.
These representations of time are mainly for internal use. If an end user interaction with dates and times is required, the software will nearly always convert this internal number into a date and time representation that is comprehensible to humans.
|
100px x 150px | 5.30kB
[source page]
Random Image EPOCH 046 Date 10 04 06 Views 82
Joe Beaudoin Jr.
Wed, 16 Jul 2008 21:18:24 GM
{{inlineref|7322}}: the [[w:. epoch. (. reference date. )|. epoch. ]] of this timeline. after one of the first cylon attacks on caprica, the people of the farm village of [[umbra]] are scattered. chameleon is separated from starbuck, ...
