"he Anno Domini dating system was devised in 525 by Dionysius Exiguus, who used it to compute the date of the Christian Easter festival, and to identify the several Easters in his Easter table, but did not use it to date any historical event. His system was to replace the Diocletian era that had been used in an old Easter table because he did not wish to continue the memory of a tyrant who persecuted Christians. The last year of the old table, Diocletian 247, was immediately followed by the first year of his table, AD 532. When he devised his table, Julian calendar years were identified by naming the consuls who held office that year Ñ he himself stated that the "present year" was "the consulship of Probus Junior", which was 525 years "since the incarnation of our Lord Jesus Christ".[7] Thus Dionysius implied 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."[2]:778 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:[2]:778Ð9 In modern times Incarnation is synonymous with the 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 [edit]Date of birth See also: Nativity of Jesus and Chronology of Jesus According to Doggett, "Although scholars generally believe that Christ was born some years before AD 1, the historical evidence is too sketchy to allow a definitive dating"[8]. According to Matthew 2:1[9] and Matthew 2:16[10], King Herod the Great was alive when Jesus was born, and ordered the Massacre of the Innocents in response to his birth. Blackburn and Holford-Strevens fix King Herod's death shortly before Passover in 4 BC[2]:770, 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 (less likely since comets were usually considered bad omens); even historians who do not accept the Massacre accept the birth under Herod as a tradition older than the written gospels.[2]:776 The Gospel of Luke states that Jesus was born during the reign of the Emperor Augustus and while Cyrenius (or Quirinius) was the governor of Syria (2:1Ð2). Blackburn and Holford-Strevens[2]:770 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 John 8:57[11]: "thou are not yet fifty years old", to place Christ's birth in circa 18 BC.[2]:776 [edit]Popularization The Anglo-Saxon historian the Venerable Bede, who was familiar with the work of Dionysius, used Anno Domini dating in his Ecclesiastical History of the English People, finished in 731. In this same history he also used another Latin term, "ante vero 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,[12] thus establishing the standard of not using a year zero,[13] 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).[2]:881
On the continent of Europe, Anno Domini was introduced as the era of choice of the Carolingian Renaissance by Alcuin. Its 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. According to the Catholic Encyclopedia, popes continued to date documents according to regnal years for some time, but usage of AD gradually became more common in Roman Catholic countries from the 11th to the 14th centuries.[14] Eastern Orthodox countries only began to adopt AD instead of the Byzantine calendar in 1700 when Russia did so, with others adopting it in the 19th and 20th centuries.
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.[15]"