when did we start using ce and bce
Common Era The expression has been traced back to 1615, when it first appeared in a book by Johannes Kepler as the Latin usage vulgaris aerae,[5][6] and to 1635 in English as "Vulgar Era".[b] The term "Common Era" can be found in English as early as 1708,[7] and became more widely used in the mid-19th century by Jewish academics. In the later 20th century, the use of CE and BCE was popularized in academic and scientific publications, and more generally by authors and publishers wishing to emphasize secularism or sensitivity to non-Christians, by not explicitly referencing Jesus as "Christ" and Dominus ("Lord") through use of the abbreviation[c] "AD".[9][10]
Anno Domini The Anno Domini dating system was devised in 525 by Dionysius Exiguus to enumerate the years in his Easter table. 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.[15] 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 yearâ€”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".[16] 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."[17]