Year zero

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For other uses, see Year zero (disambiguation)."0 A.D." redirects here. For the video game, see 0 A.D. (video game).

A year zero does not exist in the Anno Domini (AD) calendar year system commonly used to number years in the Gregorian calendar (nor in its predecessor, the Julian calendar); in this system, the year 1 BC is followed directly by year AD 1 . However, there is a year zero in both the astronomical year numbering system (where it coincides with the Julian year 1 BC), and the ISO 8601:2004 system, the interchange standard for all calendar numbering systems (where year zero coincides with the Gregorian year 1 BC; see conversion table). There is also a year zero in most Buddhist and Hindu calendars.

Contents

History

The Anno Domini era was introduced in 525 by Scythian monk Dionysius Exiguus (c. 470 – c. 544), who used it to identify the years on his Easter table. He introduced the new era to avoid using the Diocletian era , based on the accession of Roman Emperor Diocletian, as he did not wish to continue the memory of a persecutor of Christians. In the preface to his Easter table, Dionysius stated that the "present year" was "the consulship of Probus Junior" which was also 525 years "since the incarnation of our Lord Jesus Christ". [1] How he arrived at that number is unknown. [2]

Dionysius Exiguus did not use 'AD' years to date any historical event. This practice began with the English cleric Bede (c. 672–735), who used AD years in his Historia ecclesiastica gentis Anglorum (731), popularizing the era. Bede also used - only once - a term similar to the modern English term 'before Christ', though the practice did not catch on for nearly a thousand years, when books by Dionysius Petavius treating calendar science gained popularity. Bede did not sequentially number days of the month, weeks of the year, or months of the year. However, he did number many of the days of the week using the counting origin one in Ecclesiastical Latin.[ citation needed ]

Previous Christian histories used several titles for dating events: anno mundi ("in the year of the world") beginning on the purported first day of creation; or anno Adami ("in the year of Adam") beginning at the creation of Adam five days later (or the sixth day of creation according to the Genesis creation narrative) as used by Africanus; or anno Abrahami ("in the year of Abraham") beginning 3,412 years after Creation according to the Septuagint, used by Eusebius of Caesarea; all of which assigned "one" to the year beginning at Creation, or the creation of Adam, or the birth of Abraham, respectively. Bede continued this earlier tradition relative to the AD era.[ citation needed ]

In chapter II of book I of Ecclesiastical History, Bede stated that Julius Caesar invaded Britain "in the year 693 after the building of Rome, but the sixtieth year before the incarnation of our Lord", while stating in chapter III, "in the year of Rome 798, Claudius" also invaded Britain and "within a very few days ... concluded the war in ... the forty-sixth [year] from the incarnation of our Lord". [3] Although both dates are wrong, they are sufficient to conclude that Bede did not include a year zero between BC and AD: 798 − 693 + 1 (because the years are inclusive) = 106, but 60 + 46 = 106, which leaves no room for a year zero. The modern English term "before Christ" (BC) is only a rough equivalent, not a direct translation, of Bede's Latin phrase ante incarnationis dominicae tempus ("before the time of the lord's incarnation"), which was itself never abbreviated. Bede's singular use of 'BC' continued to be used sporadically throughout the Middle Ages.[ citation needed ]

Neither the concept of nor a symbol for zero existed in the system of Roman numerals. The Babylonian system of the BC era had used the idea of "nothingness" without considering it a number, and the Romans enumerated in much the same way. Wherever a modern zero would have been used, Bede and Dionysius Exiguus did use Latin number words, or the word nulla (meaning "nothing") alongside Roman numerals. [1] [4] [5] Zero was invented in India in the sixth century, and was either transferred or reinvented by the Arabs by about the eighth century. The Arabic numeral for zero (0) did not enter Europe until the thirteenth century. Even then, it was known only to very few, and only entered widespread use in Europe by the seventeenth century.[ citation needed ]

The anno Domini nomenclature was not widely used in Western Europe until the 9th century, and the 1 January to 31 December historical year was not uniform throughout Western Europe until 1752. The first extensive use (hundreds of times) of 'BC' occurred in Fasciculus Temporum by Werner Rolevinck in 1474, alongside years of the world (anno mundi). [6] The terms anno Domini, Dionysian era, Christian era, vulgar era, and common era were used interchangeably between the Renaissance and the 19th century, at least in Latin. But vulgar era fell out of use in English at the beginning of the 20th century after vulgar acquired the meaning of "offensively coarse", replacing its original meaning of "common" or "ordinary". Consequently, historians regard all these eras as equal.[ citation needed ]

Historians have never included a year zero. This means that between, for example, 1 January500 BC and 1 JanuaryAD 500, there are 999 years: 500 years BC, and 499 years AD preceding 500. In common usage anno Domini 1 is preceded by the year 1 BC, without an intervening year zero. [7] Neither the choice of calendar system (whether Julian or Gregorian) nor the name of the era (Anno Domini or Common Era) determines whether a year zero will be used. If writers do not use the convention of their group (historians or astronomers), they must explicitly state whether they include a year 0 in their count of years, otherwise their historical dates will be misunderstood. [8]

Astronomy

In astronomy, for the year AD 1 and later it is common to assign the same numbers as the Anno Domini notation, which in turn is numerically equivalent to the Common Era notation. But the discontinuity between 1 AD and 1 BC makes it cumbersome to compare ancient and modern dates. So the year before 1 AD is designated 0, the year before 0 is −1, and so on.

The letters "AD", "BC", "CE", or "BCE" are omitted. So 1 BC in historical notation is equivalent to 0 in astronomical notation, 2 BC is equivalent to −1, etc. Sometimes positive years are preceded by the + sign. This year numbering notation was introduced by the astronomer Jacques Cassini in 1740. [9]

History of astronomical usage

In 1627, the German astronomer Johannes Kepler, in his Rudolphine Tables , first used an astronomical year essentially as a year zero. He labeled it Christi and inserted it between years labeled Ante Christum and Post Christum—abbreviated BC and AD today, respectively—on the "mean motion" pages of the Sun, Moon, and planets. [10] In 1702, the French astronomer Philippe de la Hire labeled a year as Christum0 and placed it at the end of the years labeled ante Christum (BC), and immediately before the years labeled post Christum (AD), on the mean motion pages in his Tabulæ Astronomicæ, thus adding the number designation 0 to Kepler's Christi. [11]

Finally, in 1740, the transition was completed by French astronomer Jacques Cassini (Cassini II), who is traditionally credited with inventing year zero. [12] In his Tables astronomiques, Cassini labeled the year simply as 0, and placed it at the end of years labeled avant Jesus-Christ (BC), and immediately before years labeled après Jesus-Christ (AD). [13]

ISO 8601

ISO 8601:2004 (and previously ISO 8601:2000, but not ISO 8601:1988) explicitly uses astronomical year numbering in its date reference systems. (Because it also specifies the use of the proleptic Gregorian calendar for all years before 1582, some readers incorrectly assume that a year zero is also included in that proleptic calendar, but it is not used with the BC/AD era.) The "basic" format for year 0 is the four-digit form 0000, which equals the historical year 1 BC. Several "expanded" formats are possible: −0000 and +0000, as well as five- and six-digit versions. Earlier years are also negative four-, five- or six-digit years, which have an absolute value one less than the equivalent BC year, hence -0001 = 2 BC. Because only ISO 646 (7-bit ASCII) characters are allowed by ISO 8601, the minus sign is represented by a hyphen-minus.

Computing

Programming libraries may implement a year zero, an example being the Perl CPAN module DateTime. [14]

Indian calendars

Most eras used with Hindu and Buddhist calendars, such as the Saka era or the Kali Yuga, begin with the year 0. These calendars mostly use elapsed, expired, or complete years, in contrast with most calendars from other parts of the world which use current years. A complete year had not yet elapsed for any date in the initial year of the epoch, thus the number 1 cannot be used. Instead, during the first year the indication of 0 years (elapsed) is given in order to show that the epoch is less than 1 year old. This is similar to the Western method of stating a person's age – people do not reach age one until one year has elapsed since birth (but their age during the year beginning at birth is specified in months or fractional years, not as age zero). However, if ages were specified in years and months, such a person would be said to be, for example, 0 years and 6 months or 0.5 years old. This is analogous to the way time is shown on a 24-hour clock: during the first hour of a day, the time elapsed is 0 hours, n minutes.

See also

Related Research Articles

<i>Anno Domini</i> Western calendar era

The terms anno Domini (AD) and before Christ (BC) are used when designating years in the Julian and Gregorian calendars. The term anno Domini is Medieval Latin and means "in the year of the Lord" but is often presented using "our Lord" instead of "the Lord", taken from the full original phrase "anno Domini nostri Jesu Christi", which translates to "in the year of our Lord Jesus Christ". The form "BC" is specific to English, and equivalent abbreviations are used in other languages: the Latin form, rarely used in English, is Ante Christum natum (ACN) or Ante Christum (AC).

Astronomical year numbering is based on AD/CE year numbering, but follows normal decimal integer numbering more strictly. Thus, it has a year 0; the years before that are designated with negative numbers and the years after that are designated with positive numbers. Astronomers use the Julian calendar for years before 1582, including the year 0, and the Gregorian calendar for years after 1582, as exemplified by Jacques Cassini (1740), Simon Newcomb (1898) and Fred Espenak (2007).

<i>Ab urbe condita</i> Ancient Roman calendar era

Ab urbe condita, or anno urbis conditae, abbreviated as AUC or AVC, expresses a date in years since 753 BC, the traditional founding of Rome. It is an expression used in antiquity and by classical historians to refer to a given year in Ancient Rome. In reference to the traditional year of the foundation of Rome, the year 1 BC would be written AUC 753, whereas AD 1 would be AUC 754. The foundation of the Roman Empire in 27 BC would be AUC 727. The current year AD 2024 would be AUC 2777.

Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar, the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the original Anno Domini (AD) and Before Christ (BC) notations used for the same calendar era. The two notation systems are numerically equivalent: "2024 CE" and "AD 2024" each describe the current year; "400 BCE" and "400 BC" are the same year.

<span class="mw-page-title-main">ISO 8601</span> International standards for dates and times

ISO 8601 is an international standard covering the worldwide exchange and communication of date and time-related data. It is maintained by the International Organization for Standardization (ISO) and was first published in 1988, with updates in 1991, 2000, 2004, and 2019, and an amendment in 2022. The standard provides a well-defined, unambiguous method of representing calendar dates and times in worldwide communications, especially to avoid misinterpreting numeric dates and times when such data is transferred between countries with different conventions for writing numeric dates and times.

AD 1 or 1 CE(I) is the epoch year for the Anno Domini (AD) Christian calendar era, and the 1st year of the 1st century and 1st millennium of the Christian and Common Era (CE). It was a common year starting on Saturday or Sunday, a common year starting on Saturday by the proleptic Julian calendar, and a common year starting on Monday by the proleptic Gregorian calendar.

The proleptic Julian calendar is produced by extending the Julian calendar backwards to dates preceding AD 8 when the quadrennial leap year stabilized. The leap years that were actually observed between the implementation of the Julian calendar in 45 BC and AD 8 were erratic.

The Julian day is the continuous count of days since the beginning of the Julian period, and is used primarily by astronomers, and in software for easily calculating elapsed days between two events.

<span class="mw-page-title-main">1 BC</span> Calendar year

Year 1 BC was a common year starting on Friday or Saturday in the Julian calendar and a leap year starting on Thursday in the proleptic Julian calendar. It was also a leap year starting on Saturday in the Proleptic Gregorian calendar. At the time, it was known as the Year of the Consulship of Lentulus and Piso. The denomination 1 BC for this year has been used since the early medieval period when the Anno Domini calendar era became the prevalent method in Europe for naming years. The following year is AD 1 in the widely used Julian calendar, which does not have a "year zero".

<span class="mw-page-title-main">Chronology</span> Science of arranging events in order of occurrence

Chronology is the science of arranging events in their order of occurrence in time. Consider, for example, the use of a timeline or sequence of events. It is also "the determination of the actual temporal sequence of past events".

<span class="mw-page-title-main">Dionysius Exiguus</span> Byzantine saint (c. 470 – c. 544)

Dionysius Exiguus was a 6th-century Eastern Roman monk born in Scythia Minor. He was a member of a community of Scythian monks concentrated in Tomis, the major city of Scythia Minor. Dionysius is best known as the inventor of Anno Domini (AD) dating, which is used to number the years of both the Gregorian calendar and the (Christianised) Julian calendar. Almost all churches adopted his computus for the dates of Easter.

A calendar era is the period of time elapsed since one epoch of a calendar and, if it exists, before the next one. For example, it is the year 2024 as per the Gregorian calendar, which numbers its years in the Western Christian era.

Annianus of Alexandria was a monk and writer who flourished in Alexandria during the pontificate of Theophilus I around the beginning of the 5th century.

The Ethiopian calendar, or Ge'ez calendar is the official calendar of Ethiopia. It is used as both the civil calendar and an ecclesiastical calendar. It is the liturgical year for Ethiopian and Eritrean Christians belonging to the Orthodox Tewahedo Churches, Eastern Catholic Churches, and Eastern Protestant Christian P'ent'ay Churches. The Ethiopian calendar is a solar calendar that has much in common with the Coptic calendar of the Coptic Orthodox Church of Alexandria and Coptic Catholic Church, but like the Julian calendar, it adds a leap day every four years without exception, and begins the year on 11 or 12th of September in the Julian calendar. A gap of seven to eight years between the Ethiopian and Gregorian calendars results from an alternative calculation in determining the date of the Annunciation.

The Era of the Martyrs, also known as the Diocletian era, is a method of numbering years based on the reign of Roman Emperor Diocletian who instigated the last major persecution against Christians in the Empire. It was used by the Church of Alexandria beginning in the 4th century AD and it has been used by the Coptic Orthodox Church of Alexandria from the 5th century until the present. This era was used to number the year in Easter tables produced by the Church of Alexandria.

<i>Anno Mundi</i> Calendar era based on the biblical account of creation

Anno Mundi, abbreviated as AM or A.M., or Year After Creation, is a calendar era based on the biblical accounts of the creation of the world and subsequent history. Two such calendar eras have seen notable use historically:

The term ante Christum natum, usually abbreviated to a. Chr. n., a.Ch.n., a.C.n., A.C.N., or ACN, denotes the years before the birth of Jesus Christ. It is a Latin equivalent to the English "BC". The phrase ante Christum natum is also seen shortened to ante Christum, similarly abbreviated to a. Chr., A. C. or AC. A related phrase, p. Chr. n., p. Ch. n., or post Christum natum complements a. Ch. n. and is equivalent to Anno Domini (AD).

Dionysius Exiguus's Easter table was constructed in the year 525 by Dionysius Exiguus for the years 532–626. He obtained it from an Easter table attributed to Patriarch Cyril of Alexandria for the years 437–531. The latter was constructed around the year 440 by means of extrapolation from an Alexandrian Easter table constructed around the year 390 by Patriarch Theophilus of Alexandria. The great historical importance of Dionysius' Easter table is twofold:

  1. From this Easter table Bede's Easter cycle would ultimately be developed by means of which all future Julian calendar dates of Easter Sunday were determined ;
  2. With his Easter table Dionysius introduced in passing the Christian era which would be developed into a full system for dating historical events by Bede two centuries later.

The proleptic Gregorian calendar is produced by extending the Gregorian calendar backward to the dates preceding its official introduction in 1582. In nations that adopted the Gregorian calendar after its official and first introduction, dates occurring in the interim period of 15 October 1582 to the date on which the pertinent nation adopted the Gregorian calendar and abandoned the Julian calendar are sometimes 'Gregorianized' also. For example, the birthday of U.S. President George Washington was originally dated 11 February 1731 because Great Britain, of which he was born a subject, used the Julian calendar and dated the beginning of English years as 25 March. After Great Britain switched to the Gregorian calendar, Washington's birthday was dated 22 February 1732 proleptically, according to the Gregorian calendar applied backward. This remains the modern dating of his birthday.

Thailand has adopted ISO 8601 under national standard: TIS 1111:2535 in 1992. However, in practice, there are some variations.

References

  1. 1 2 "Dionysius Exiguus. Liber de paschate sive cyclus paschalis". Archived from the original on 9 January 2006.
  2. ↑ Blackburn, Bonnie; Holford-Strevens, Leofranc (2003). The Oxford Companion to the Year: An exploration of calendar customs and time-reckoning (corrected reprinting of 1999 ed.). Oxford University Press. pp. 778–779. ISBN   9780192142313.
  3. ↑ "Ecclesiastical History of the English Nation". Archived from the original on 30 August 2009. Retrieved 5 August 2005.
  4. ↑ Faith Wallis, trans. Bede: The Reckoning of Time (725), Liverpool: Liverpool University Press, 2004. ISBN   0-85323-693-3.
  5. ↑ Byrhtferth's Enchiridion (1016). Edited by Peter S. Baker and Michael Lapidge. Early English Text Society 1995. ISBN   978-0-19-722416-8.
  6. ↑ Werner Rolevinck, Fasciculus temporum Archived 10 February 2016 at the Wayback Machine .
  7. ↑ While it is increasingly common to place AD after a date by analogy to the use of BC, formal English usage adheres to the traditional practice of placing the abbreviation before the year as in Latin (e.g., 100 BC, but AD 100).
  8. ↑ V. Grumel, La chronologie (1958), page 30.
  9. ↑ Richards, E. G. (2013). "Calendars". In Urban, Sean E.; Seidelmann, P. Kenneth (eds.). Explanatory Supplement to the Astronomical Almanac (3 ed.). Mill Valley, California: University Science Books. p. 591. ISBN   978-1-891389-85-6.
  10. ↑ "Tabulae Rudolphinae – Ioannes Keplerus" Archived 11 May 2017 at the Wayback Machine (1627) 191 (42), 197 (48), 203 (54), 209 (60), 215 (66), 221 (72), 227 (78).
  11. ↑ Tabulae Astronomicae – Philippo de la Hire Archived 26 March 2023 at the Wayback Machine (1702), Tabulæ 15, 21, 39, 47, 55, 63, 71; Usus tabularum 4.
  12. ↑ Robert Kaplan, The nothing that is Archived 30 June 2023 at the Wayback Machine (Oxford: Oxford University Press, 2000) 103.
  13. ↑ [Jacques] Cassini, Tables astronomiques (1740), Explication et usage 5; Tables 10, 22, 53.
  14. ↑ "DateTime – A date and time object – metacpan.org". Archived from the original on 5 March 2020. Retrieved 2 April 2019.
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