A year zero does not exist in the
Anno Domini
The terms (AD) and before Christ (BC) are used to label or number years in the Julian and Gregorian calendars. The term is Medieval Latin and means 'in the year of the Lord', but is often presented using "our Lord" instead of "the Lord", ...
(AD) calendar year system commonly used to number years in the
Gregorian calendar
The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years di ...
(nor in its predecessor, the
Julian calendar
The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematics, Greek mathematicians and Ancient Greek astronomy, as ...
); in this system, the year is followed directly by year . However, there is a year zero in both the
astronomical year numbering
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 ...
system (where it coincides with the Julian year ), and the
ISO 8601:2004 system, the interchange standard for all calendar numbering systems (where year zero coincides with the Gregorian year ; see
conversion table
Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors which change the measured quantity value without changing its effects.
Overview
The process ...
). There is also a year zero in most
Buddhist
Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha. It originated in northern India as a -movement in the 5th century BCE, and ...
and
Hindu calendar
The Hindu calendar, Panchanga () or Panjika is one of various lunisolar calendars that are traditionally used in the Indian subcontinent and Southeast Asia, with further regional variations for social and Hindu religious purposes. They adopt a ...
s.
Historical, astronomical and ISO year numbering systems
Historians
The ''
Anno Domini
The terms (AD) and before Christ (BC) are used to label or number years in the Julian and Gregorian calendars. The term is Medieval Latin and means 'in the year of the Lord', but is often presented using "our Lord" instead of "the Lord", ...
'' era was introduced in 525 by
Scythian
The Scythians or Scyths, and sometimes also referred to as the Classical Scythians and the Pontic Scythians, were an ancient Eastern
* : "In modern scholarship the name 'Sakas' is reserved for the ancient tribes of northern and eastern Cent ...
monk
Dionysius Exiguus
Dionysius Exiguus (Latin for "Dionysius the Humble", Greek: Διονύσιος; – ) was a 6th-century Eastern Roman monk born in Scythia Minor. He was a member of a community of Scythian monks concentrated in Tomis (present day Constanța ...
(c. 470 – c. 544), who used it to identify the years on his
Easter table
As a moveable feast, the date of Easter is determined in each year through a calculation known as (). Easter is celebrated on the first Sunday after the Paschal full moon, which is the first full moon on or after 21 March (a fixed approx ...
. 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
A consul held the highest elected political office of the Roman Republic ( to 27 BC), and ancient Romans considered the consulship the second-highest level of the '' cursus honorum'' (an ascending sequence of public offices to which polit ...
of
Probus Junior lavius Anicius Probus Iunior which was also 525 years "since the incarnation of our Lord
Jesus Christ
Jesus, likely from he, יֵשׁוּעַ, translit=Yēšūaʿ, label=Hebrew/Aramaic ( AD 30 or 33), also referred to as Jesus Christ or Jesus of Nazareth (among other names and titles), was a first-century Jewish preacher and religious ...
".
How he arrived at that number is unknown.
Dionysius Exiguus did not use 'AD' years to date any historical event. This practice began with the English cleric
Bede
Bede ( ; ang, Bǣda , ; 672/326 May 735), also known as Saint Bede, The Venerable Bede, and Bede the Venerable ( la, Beda Venerabilis), was an English monk at the monastery of St Peter and its companion monastery of St Paul in the Kingdom ...
(c. 672–735), who used AD years in his (731), popularizing the era. Bede also used - only once - a term similar to the modern English term '
before Christ
The terms (AD) and before Christ (BC) are used to label or number years in the Julian and Gregorian calendars. The term is Medieval Latin and means 'in the year of the Lord', but is often presented using "our Lord" instead of "the Lord", ...
', 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
A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours, 1440 minutes, or 86,400 seconds. In everyday life, the word "day" often refers to a solar day, which is the length between two so ...
using the counting origin one in
Ecclesiastical Latin
Latin, also called Church Latin or Liturgical Latin, is a form of Latin developed to discuss Christian thought in Late Antiquity and used in Christian liturgy, theology, and church administration down to the present day, especially in the Ca ...
.
Previous Christian histories used several titles for dating events: ("in the year of the world") beginning on the purported first day of
creation
Creation may refer to:
Religion
*'' Creatio ex nihilo'', the concept that matter was created by God out of nothing
*Creation myth, a religious story of the origin of the world and how people first came to inhabit it
*Creationism, the belief that ...
; or ("in the year of
Adam
Adam; el, Ἀδάμ, Adám; la, Adam is the name given in Genesis 1-5 to the first human. Beyond its use as the name of the first man, ''adam'' is also used in the Bible as a pronoun, individually as "a human" and in a collective sense as " ...
") 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 ("in the year of
Abraham
Abraham, ; ar, , , name=, group= (originally Abram) is the common Hebrews, Hebrew patriarch of the Abrahamic religions, including Judaism, Christianity, and Islam. In Judaism, he is the founding father of the Covenant (biblical), special ...
") beginning 3,412 years after Creation according to the
Septuagint
The Greek Old Testament, or Septuagint (, ; from the la, septuaginta, lit=seventy; often abbreviated ''70''; in Roman numerals, LXX), is the earliest extant Greek translation of books from the Hebrew Bible. It includes several books beyond t ...
, 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.
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
earfrom 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. The modern English term "before Christ" (BC) is only a rough equivalent, ''not'' a direct translation, of Bede's Latin phrase ("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
In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
.
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
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...
number words, or the word (meaning "nothing") alongside Roman numerals.
[ 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.
The nomenclature was not widely used in ]Western Europe
Western Europe is the western region of Europe. The region's countries and territories vary depending on context.
The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the ancient Mediterranean ...
until the 9th century, and the to historical year was not uniform throughout Western Europe until 1752. The first extensive use (hundreds of times) of 'BC' occurred in by Werner Rolevinck in 1474, alongside years of the world (). The terms ''anno Domini'', ''Dionysian era'', ''Christian era'', ''vulgar era'', and ''common era'' were used interchangeably between the Renaissance
The Renaissance ( , ) , from , with the same meanings. is a period in European history marking the transition from the Middle Ages to modernity and covering the 15th and 16th centuries, characterized by an effort to revive and surpass id ...
and the 19th century, at least in Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...
. 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.
Historians have never included a year zero. This means that between, for example, and , 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. Neither the choice of calendar system (whether Julian
Julian may refer to:
People
* Julian (emperor) (331–363), Roman emperor from 361 to 363
* Julian (Rome), referring to the Roman gens Julia, with imperial dynasty offshoots
* Saint Julian (disambiguation), several Christian saints
* Julian (give ...
or Gregorian) nor the name of the era (''Anno Domini'' or Common Era
Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the ...
) 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.
Astronomers
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.
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 and BC and AD today, on the "mean motion" pages of the Sun, Moon, and planets. In 1702, the French astronomer Philippe de la Hire labeled a year as and placed it at the end of the years labeled (BC), and immediately before the years labeled (AD), on the mean motion pages in his , thus adding the number designation ''0'' to Kepler's .
Finally, in 1740, the transition was completed by French astronomer Jacques Cassini , who is traditionally credited with inventing year zero. In his , Cassini labeled the year simply as ''0'', and placed it at the end of years labeled (BC), and immediately before years labeled (AD).
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
ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because ...
) characters are allowed by ISO 8601, the minus sign is represented by a hyphen-minus
The hyphen-minus is the most commonly used type of hyphen, widely used in digital documents. It is the only character that looks like a minus sign or a dash in many character sets such as ASCII or on most keyboards, so it is also used as suc ...
.
Computing
Programming libraries may implement a year zero, an example being the Perl CPAN module DateTime.DateTime – A date and time object – metacpan.org
/ref>
South Asian calendars
Most eras used with Hindu and Buddhist calendars, such as the Saka era or the Kali Yuga
''Kali Yuga'', in Hinduism, is the fourth and worst of the four '' yugas'' (world ages) in a '' Yuga Cycle'', preceded by ''Dvapara Yuga'' and followed by the next cycle's '' Krita (Satya) Yuga''. It is believed to be the present age, which ...
, 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
The modern 24-hour clock, popularly referred to in the United States as military time, is the convention of timekeeping in which the day runs from midnight to midnight and is divided into 24 hours. This is indicated by the hours (and minutes) pas ...
: during the first hour of a day, the time elapsed is 0 hours, ''n'' minutes.
See also
* January 0
References
{{Calendars
Chronology
Astronomical coordinate systems
zero
0 (zero) is a number representing an empty quantity. In place-value notation such as the Hindu–Arabic numeral system, 0 also serves as a placeholder numerical digit, which works by multiplying digits to the left of 0 by the radix, usu ...
0 (number)
0s
0s BC
Nonexistent things