Anno domini system of dating
When the reckoning from Jesus' incarnation started replacing the previous dating systems in western Europe, different people chose different Christian feast days to begin the year: Christmas, Annunciation, or Easter.
in 1505 for us) and on 12 April 1506, but not in 1505., 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.
Tiberius began to reign with his father, Augustus, in AD 12.
The 15th year of his reign would then be 26 or 27 AD, placing Jesus' birth about 5 or 4 BC (because there is no year 0).
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—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"."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." The Anglo-Saxon historian the Venerable Bede, who was familiar with the work of Dionysius Exiguus, used Anno Domini dating in his Ecclesiastical History of the English People, finished in 731.
Traditionally, English has copied Latin usage by placing the abbreviation before the year number for AD.