Anno Domini ( Medieval Latin: In the year of (the/Our) Lord), abbreviated as AD or A.D., is a designation used to number years in the Julian and Gregorian calendars. More fully, years may be also specified as Anno Domini Nostri Iesu (Jesu) Christi ("In the Year of Our Lord Jesus Christ").
The calendar era which it numbers is based on the traditionally reckoned year of the conception or birth of Jesus. Before Christ, abbreviated as BC or B.C., is used in the English language to denote years before the start of this epoch.
Though the Anno Domini dating system was devised in 525, it was not until the 8th century that the system began to be adopted in Western Europe. According to the Catholic Encyclopedia, even popes continued to date documents according to regnal years, and usage of AD only gradually became more common in Europe from the 11th to the 14th centuries. In 1422, Portugal became the last Western European country to adopt the Anno Domini system.
Year numbering using the Anno Domini system (or its related Common Era (CE) designation) is the most widespread numbering system in the world today. For decades, it has been the unofficial global standard, recognized by international institutions such as the United Nations and the Universal Postal Union. Its preeminence is due to the European colonisation of the Americas and the subsequent global spread of Western civilization with the introduction of European standards in the fields of science and administration. Its association with the Gregorian calendar was another factor which promoted the spread of the numbering system.
Traditionally, English copied Latin usage by placing the abbreviation before the year number for AD, but after the year number for BC; for example: 64 BC, but AD 2013. However, placing the AD after the year number (as in 2013 AD) is now also common. The abbreviation is also widely used after the number of a century or millennium, as in 4th century AD or 2nd millennium AD, despite the inappropriate literal combination in this case ("in the 4th century in the year of Our Lord").
Because B.C. is an abbreviation for Before Christ, some people incorrectly conclude that A.D. must mean After Death, i.e., after the death of Jesus. If that were true, the thirty-three or so years of his life wouldn't be in any era.
During the first six centuries of what would come to be known as the Christian era, European countries used various systems to count years. Systems in use included consular dating, imperial regnal year dating, and Creation dating.
Although the last non-imperial consul, Basilius, was appointed in 541 by Emperor Justinian I, later emperors through Constans II (641–668) were appointed consuls on the first January 1 after their accession. All of these emperors, except Justinian, used imperial postconsular years for all of the years of their reign alongside their regnal years. Long unused, this practice was not formally abolished until Novell xciv of the law code of Leo VI did so in 888.
The Anno Domini system was devised by a monk named Dionysius Exiguus (born in Scythia Minor) in Rome in 525. In his Easter table Dionysius equates the year AD 532 with the regnal year 284 of Emperor Diocletian. In Argumentum I attached to this table he equates the year AD 525 with the consulate of Probus Junior. He thus implies that Jesus' Incarnation occurred 525 years earlier, without stating the specific year during which his birth or conception occurred.
- "However, nowhere in his exposition of his table does Dionysius relate his epoch to any other dating system, whether consulate, Olympiad, year of the world, or regnal year of Augustus; much less does he explain or justify the underlying date."
Blackburn & Holford-Strevens briefly present arguments for 2 BC, 1 BC, or AD 1 as the year Dionysius intended for the Nativity or Incarnation.
Among the sources of confusion are:
- In modern times Incarnation is synonymous with conception, but some ancient writers, such as Bede, considered Incarnation to be synonymous with the Nativity
- The civil, or consular year began on January 1 but the Diocletian year began on August 29
- There were inaccuracies in the list of consuls
- There were confused summations of emperors' regnal years
Two centuries later, the Anglo-Saxon historian Bede the Venerable used another Latin term, "ante uero incarnationis dominicae tempus" ("the time before the Lord's true incarnation"), equivalent to the English "before Christ", to identify years before the first year of this era.
Another calculation had been developed by the Alexandrian monk Annianus around the year AD 400, placing the Annunciation on March 25, AD 9 (Julian)—eight to ten years after the date that Dionysius was to imply. Although this Incarnation was popular during the early centuries of the Byzantine Empire, years numbered from it, an Era of Incarnation, was only used, and is still only used, in Ethiopia, accounting for the eight- or seven-year discrepancy between the Gregorian and the Ethiopian calendars. Byzantine chroniclers like Maximus the Confessor, George Syncellus and Theophanes dated their years from Annianus' Creation of the World. This era, called Anno Mundi, "year of the world" (abbreviated AM), by modern scholars, began its first year on 25 March 5492 BC. Later Byzantine chroniclers used Anno Mundi years from September 1 5509 BC, the Byzantine Era. No single Anno Mundi epoch was dominant throughout the Christian world.
According to Doggett, "Although scholars generally believe that Christ was born some years before A.D. 1, the historical evidence is too sketchy to allow a definitive dating". According to the Gospel of St. Matthew (2:1,16) King Herod the Great was alive when Jesus was born, and ordered the Massacre of the Innocents in response to his birth. Blackburn & Holford-Strevens fix King Herod's death shortly before Passover in 4 BC, and say that those who accept the story of the Massacre of the Innocents sometimes associate the star that led the Biblical Magi with the planetary conjunction of September 15 7 BC or Halley's comet of 12 BC; even historians who do not accept the Massacre accept the birth under Herod as a tradition older than the written gospels.
The Gospel of St. Luke (1:5) states that St. John the Baptist was at least conceived, if not born, under King Herod, and that Jesus was conceived while St. John's mother St. Elizabeth was in the sixth month of her pregnancy (1:26). St. Luke's Gospel also states that Jesus was born during the reign of the Emperor Augustus and while Cyrenius (or Quirinius) was the governor of Syria (2:1–2). Blackburn and Holford-Strevens indicate Cyrenius/Quirinius' governorship of Syria began in AD 6, which is incompatible with conception in 4 BC, and say that "St. Luke raises greater difficulty....Most critics therefore discard Luke". Some scholars rely on St. John's Gospel to place Christ's birth in c. 18 BC.
The first historian or chronicler to use Anno Domini as his primary dating mechanism was Victor of Tonnenna, an African chronicler of the 6th century. A few generations later, the Anglo-Saxon historian Bede the Venerable, who was familiar with the work of Dionysius, also used Anno Domini dating in his Ecclesiastical History of the English People, finished in 731. In this same history, he was the first to use the Latin equivalent of before Christ and established the standard for historians of no year zero, even though he used zero in his computus. Both Dionysius and Bede regarded Anno Domini as beginning at the incarnation of Jesus, but "the distinction between Incarnation and Nativity was not drawn until the late 9th century, when in some places the Incarnation epoch was identified with Christ's conception, i.e., the Annunciation on March 25" (Annunciation style).
On the continent of Europe, Anno Domini was introduced as the era of choice of the Carolingian Renaissance by Alcuin. This endorsement by Emperor Charlemagne and his successors popularizing the usage of the epoch and spreading it throughout the Carolingian Empire ultimately lies at the core of the system's prevalence until present times.
Outside the Carolingian Empire, Spain continued to date by the Era of the Caesars, or Spanish Era, which began counting from 38 BC, well into the Middle Ages,. The Era of Martyrs, which numbered years from the accession of Diocletian in 284, who launched the last yet most severe persecution of Christians, was used by the Church of Alexandria, and is still used officially by the Coptic church. It also used to be used by the Ethiopian church. Another system was to date from the crucifixion of Jesus Christ, which as early as Hippolytus and Tertullian was believed to have occurred in the consulate of the Gemini (AD 29), which appears in the occasional medieval manuscript. Most Syriac manuscripts written at the end of the 19th century still gave the date in the end-note using the "year of the Greeks" (Anno Graecorum = Seleucid era).
Even though Anno Domini was in widespread use by the 9th century, Before Christ (or its equivalent) did not become widespread until the late 15th century.
Anno Domini is sometimes referred to as the Common Era, Christian Era or Current Era (abbreviated as C.E. or CE). CE is often preferred by those who desire a term unrelated to religious conceptions of time. For example, Cunningham and Starr (1998) write that "B.C.E./C.E. ... do not presuppose faith in Christ and hence are more appropriate for interfaith dialog than the conventional B.C./A.D." The People's Republic of China, founded in 1949, adopted Western years, calling that era gōngyuán (公元) which literally means Common Era.
Anno Salutis (Latin: "in the year of salvation") was the term sometimes used in place of Anno Domini until the 18th century. In all other respects it operated on the same epoch, reference date, which is the Incarnation of Jesus. It was used by fervent Christians to spread the message that the birth of Jesus saved mankind from eternal damnation. It was often used in a more elaborate form such as Anno Nostrae Salutis (meaning: "in the year of our salvation"), Anno Salutis Humanae (meaning: "in the year of the salvation of men"), or Anno Reparatae Salutis (meaning: "in the year of accomplished salvation").
Numbering of years
Common usage omits year zero. This creates a problem with some scientific calculations. Accordingly, in astronomical year numbering, a zero year is added before AD 1, and the 'AD' and 'BC' designation is dropped. In keeping with 'standard decimal numbering', a minus sign '−' is added for years before year zero: so counting down from year 2 would give 2, 1, 0, −1, −2, and so on. This results in a one-year shift between the two systems (eg −1 equals 2 BC).