0 (year)

From Academic Kids


The presence or absence of year 0 is determined by convention among a group of writers such as historians or astronomers. Neither the calendar (Julian or Gregorian) nor the era (Anno Domini or Common Era) determines that. If writers do not use the convention of their group, they must explicitly state whether or not they include a year 0 in their count of years, otherwise their historical dates will be misunderstood.

Virtually all modern historians (including Wikipedia) do not include a year 0 when numbering years. Thus 1 BC or 1 BCE immediately precedes AD 1 or 1 CE, regardless of the calendar. Note that the anno Domini method of numbering years was not widely used in Western Europe until the ninth century, and the 1 January to 31 December historical year was not uniform throughout Western Europe until 1752. The terms anno Domini, common era, and vulgar era were used interchangeably between the Renaissance and the nineteenth century, at least in Latin. But vulgar era was suppressed in English at the beginning of the twentieth century after vulgar acquired the meaning of "offensively coarse", replacing its original meaning of "common" or "ordinary". Consequently, historians regard all three eras as equal.

However, at least two groups do include a year 0 when they number the years before these eras, astronomers and some Maya historians. In addition, some calendars of South Asia begin their counts of years with a year 0.



Bede was the first historian to use a BC year and hence the first to adopt the convention of no year 0 between BC and AD, in his Historia ecclesiastica gentis Anglorum (Ecclesiastical history of the English people, 731). Previous Christian histories used anno mundi (in the year of the world"), or anno Adami ("in the year of Adam", beginning five days later, used by Africanus), or anno Abrahami ("in the year of Abraham", beginning 3,412 years later according to the Septuagint, used by Eusebius), all of which assigned "one" to the year beginning at Creation, or the creation of Adam, or the birth of Abraham, respectively. All began with year one because the counting numbers begin with one, not zero. Bede simply continued this earlier tradition relative to the AD era. The inventor of AD, Dionysius Exiguus in 525, did not specify whether he began his count at one or zero (nor did he mention BC). Even though Bede did not begin his count at zero, he was well aware of zero as a number because zero was the first epact of the nineteen-year cycle used to calculate the date of Easter, as he explained in his De temporum ratione (On the reckoning of time, 725). Here, Bede was simply repeating the earlier use of this zero epact by Dionysius. The Latin word nulla meaning "nothing" was used for this zero epact, whereas other epacts were numbered via Roman numerals or Latin words.

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 fortysixth [year] from the incarnation of our Lord". 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. Note well that the English term "before Christ" (BC) is not a direct translation of the Latin term "before/from the incarnation of our Lord" (itself never abbreviated), but is only a rough equivalent: Incarnation means the conception of Christ, which has been on 25 March since the fourth century, nine months before his birth on 25 December. Bede's singular use of 'BC' continued to be used sporadically throughout the Middle Ages (albeit with a correct year). The first extensive use of 'BC' (hundreds of times) occurred in Fasciculus Temporum by Werner Rolevinck in 1474, alongside years of the world (anno mundi).


Astronomers include a year 0 immediately before year 1. The first use of an astronomical year 0 is traditionally attributed to Jacques Cassini in his Tables astronomiques (Astronomical Tables, 1740) wherein he explained his reasons for doing so. But Phillipe de La Hire had used it earlier in 1702 in his Tabulć Astronomicć (Astronomical Tables) in the form Christum o. ("Christ 0"), without explanation. Both Cassini and La Hire used BC years before their year 0 and AD years thereafter (hence the sequence 1 BC, 0, AD 1). Beginning in the nineteenth century, some astronomers began to use negative years before their year 0, while other astronomers continued to use BC years before their year 0. By the mid twentieth century, all astronomers were using negative years before year 0 (hence the sequence -1, 0, 1). Although 'AD' is omitted from later years, leaving a bare number, a positive sign (+) is sometimes explicitly prefixed to the number. Because of possible confusion with the earlier use of an astronomical BC, only in the modern version can it be said that astronomical year 0 equals the historical year 1 BC.

ISO 8601:2004 and ISO 8601:2000, but not ISO 8601:1988, explicitly use astronomical year numbering in their date reference systems. The "basic" format for year zero 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, the minus signs are hyphens.

In Wikipedia date preferences, the only zero year which is properly converted and linked to 1 BC (and vice-versa) is the ISO year -0000. A bug (or 'feature') causes the ISO basic year of 0000 to be converted and linked to 0. In the opposite direction, 0 is converted to the ISO year 0000 but linked to 0, whereas 0000 is converted to the ISO year 0000 and linked to 0000, redirected to 1 BC. Years can only be converted if an "extended" ISO format of [[YYYY-MM-DD]] or an expanded, extended format of [[-YYYY-MM-DD]] is used. No other ISO date format is an allowable date preference in Wikipedia. Although the isolated year [[0000]] is redirected to 1 BC, [[0]] is not — neither isolated year is converted.

South Asian calendars

All eras used with Hindu and Buddhist calendars, such as the Saka era or the Kali Yuga, begin with a year zero because all of these calendars use elapsed, expired, or complete years, in contrast with most other calendars which use current years. A complete year had not yet elapsed for any date in the year beginning at the epoch, thus that could not be year one — instead, it was year zero. 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, not as age zero).

Maya historians

Many Maya historians, but not all, assume (or used to assume) that a year zero exists in the modern calendar and thus specify that the epoch of the Long Count of the Maya calendar occurred in 3113 BC rather than 3114 BC. Note that this would require the sequence 1 BC, 0, AD 1 as in early astronomical years.

Third millennium

Historians argued that the third millennium began 1 January 2001 because their historical years do not include a year 0, whereas most people assumed that it began 1 January 2000 because that was when the most significant digit of the year changed (1 → 2). Astronomical year numbering cannot be used to support year 2000 as the first year of the third millennium because of uncertainty regarding astronomical millennia. Including year 0 in the first positive millennium (0 to 999) while excluding it from the first negative millennium (-1000 to -1) would be inconsistent. But consistency produces unusual results: either year 0 separates the first positive millennium (1 to 1000) from the first negative millennium (-1000 to -1) or it is included in both (-999 to 0 to 999).


In the movie Back to the Future, Dr. Emmett Brown, the inventor of a time machine, enters the date of the "birth of Christ" on a keypad as December 25, 0000. Not only does he use the astronomical year number, but he assumes that Jesus was actually born in that year (he was born between 8 BC and AD 9, according to different sources), and also that Christianity's celebration of Christmas on December 25 is a true historical anniversary rather than a traditional date. (Of course, it's possible that he was just being funny and/or showing off.)

The famous and ficticious theologian Franz Bibfeldt's most famous work relates to the year 0: a 1927 dissertation submission to the University of Worms entitled "The Problem of the Year 0."

External link

de:Jahr Null et:0. aasta es:0 eo:Kial Ne Estas Jaro 0 fr:Année zéro ko:0년 it:Anno 0 nl:0 no:0 sl:0 (leto) fi:Vuosi 0 sv:0


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