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Anno Domini ^[1] (pronounced /ˈænoʊ ˈdɒmɪnaɪ/ by speakers of English; Latin: In the year of (Our) Lord),^[2] abbreviated as AD or A.D., defines an epoch based on the traditionally reckoned year of the conception (Annunciation) or birth of Jesus of Nazareth. Similarly, Before Christ (from the Ancient Greek "Christos" or "Anointed One", referring to Jesus), abbreviated as BC or B.C., is used in the English language to denote years before the start of this epoch.

The designation is used to number years in the Christian Era, conventionally used with the Julian and Gregorian calendars.^[3] More fully, years may be also specified as Anno Domini Nostri Iesu (Jesu) Christi ("In the Year of Our Lord Jesus Christ").

Though the Anno Domini dating system was devised in 525 it was not until the 8th century that the system began being 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.^[4] In 1422, Portugal became the last Western European country to adopt the Anno Domini system.^[4]

Year numbering using the Anno Domini system (or its related 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 historical processes of European imperialism, by means of which the Christian calendar came to be imposed upon those who wanted to be recognized as members of the modern world. Its association with the Gregorian calendar is another factor which promoted the spread of the numbering system.

Traditionally English copies 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 2007. However, the placing of the AD after the year number (as in 2007 AD) is now also common, while, analogous to the use of BC, 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").

Contents 1 History 1.1 Accuracy 1.2 Popularization 2 Synonyms 2.1 Common Era 2.2 Anno Salutis 3 Numbering of years 4 See also 5 Notes 6 References 7 External links

Further information: Calendar 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.

The use of consular dating ended in 541 when the emperor Justinian I discontinued appointing consuls. The last consul nominated was Anicius Faustus Albinus Basilius. Soon after, imperial regnal dating was adopted in its place. The papacy was in regular contact throughout the Middle Ages with envoys of the Byzantine world, and had a clear idea—sudden deaths and deposals notwithstanding—of who the Byzantine emperor was at any one time.

The Anno Domini system was devised by a monk named Dionysius Exiguus (born in Scythia Minor) in Rome in 525. It arose from his efforts to calculate the date of Easter. In his Easter table Dionysius equates the year AD 532 with the regnal year 284 of Emperor Diocletian. In his cover letter he equates the year AD 525 with the consulate of Probus Junior.

"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."^[5]

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:^[6]

• 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 1 January but the Diocletian year began on 29 August
• There were inaccuracies in the list of consuls
• There were confused summations of emperors' regnal years

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 calculate. This Era of Incarnation was dominant in the eastern part of the Roman world during the early centuries of the Byzantine Empire, and is still used today in Ethiopia, accounting for the eight- or seven-year discrepancy between the Gregorian and the Ethiopian calendars.

Byzantine chroniclers like Theophanes continued to date each year in their world chronicles on a different Judaeo-Christian basis—from the notional creation of the World as calculated by Christian scholars in the first five centuries of the Christian era. These eras, sometimes called Anno Mundi, "year of the world" (abbreviated AM), by modern scholars, had their own disagreements. No single Anno Mundi epoch was dominant. One popular formulation was that established by Eusebius of Caesarea, a historian at the time of Constantine I. The Latin translator Jerome helped popularize Eusebius's AM count in the West.

Two centuries later, the Anglo-Saxon historian Bede 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.^[7]

"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".^[8] According to the Gospel of Matthew (2:1,16) 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 Herod's death shortly before Passover in 4 BC,^[9] 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 15 September 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.^[10]

The Gospel of Luke (1:5) states that John the Baptist was at least conceived, if not born, under Herod, and that Christ was conceived while John's mother was in the sixth month of her pregnancy (1:26). Luke's Gospel also states that Christ was born during the reign of Augustus and while Cyrenius (or Quirinius) was the governor of Syria (2:1–2). Blackburn and Holford-Strevens^[9] 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".^[10] Some scholars rely on John's Gospel to place Christ's birth in c.18 BC.^[10]

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, 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 25 March" (Annunciation style).^[11]

On the continent of Europe, Anno Domini was introduced as the era of choice of the Carolingian Renaissance by Alcuin. This endorsement by 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, well into the Middle Ages, which began counting from 38 BC. The Era of Martyrs, which numbered years from the accession of Diocletian in 284, who launched the last yet most severe persecution of Christians, prevailed in the Eastern part of the Empire, 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).^{[citation needed]}

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.

Main article: Common Era

Anno Domini is sometimes referred to as the Common Era (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 Christ. 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").

Historians do not use a year zero—AD 1 is the first year or epoch of the Anno Domini numbering system, and 1 BC immediately precedes it as the first year before the epoch.

Common usage omits year zero. This creates a problem with some scientific calculations. Accordingly, in astronomical year numbering, a zero year is added before 1 AD, 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).

• Astronomical year numbering
• Calendar
• Chronology

• Abate, Frank R(ed.) (1997). Oxford Pocket Dictionary and Thesaurus, American ed., New York: Oxford University Press. ISBN 0-19-513097-9. 
• Bede. (731). Historiam ecclesiasticam gentis Anglorum. Accessed 2007-12-07.
• Blackburn, Bonnie; Leofranc Holford-Strevens (2003). The Oxford companion to the Year: An exploration of calendar customs and time-reckoning. Oxford: Oxford University Press. ISBN 0-19-214231-3.  (reprinted & corrected, originally published 1999)
• Cunningham, Philip A; Starr, Arthur F (1998). Sharing Shalom: A Process for Local Interfaith Dialogue Between Christians and Jews. Paulist Press. ISBN 0-8091-3835-2. 
• Declercq, Georges (2000). Anno Domini: The origins of the Christian era. Turnhout: Brepols. ISBN 2-503-51050-7.  (despite beginning with 2, it is English)
• Declercq, G. "Dionysius Exiguus and the Introduction of the Christian Era". Sacris Erudiri 41 (2002): 165–246. An annotated version of part of Anno Domini.
• Doggett. (1992). "Calendars" (Ch. 12), in P. Kenneth Seidelmann (Ed.) Explanatory supplement to the astronomical almanac. Sausalito, CA: University Science Books. ISBN 0-935702-68-7.
• Richards, E. G. (2000). Mapping Time. Oxford: Oxford University Press. ISBN 0-19-286205-7. 
• Riggs, John (January-February 2003). Whatever happened to B.C. and A.D., and why?. United Church News. Retrieved on December 19, 2005.
• TaiwanCalender Class (System.Globalization). Microsoft Corp. (2006). Retrieved on September 10, 2006.

• The Catholic Encyclopedia, s.v. "General Chronology"