Ante Christum natum


The term ante Christum natum, usually abbreviated to a. Chr. n., a.Ch.n., a.C.n., A.C.N., or ACN, denotes the years before the birth of Jesus Christ. It is a Latin equivalent to the English "BC". The phrase ante Christum natum is also seen shortened to ante Christum, similarly abbreviated to a. Chr., A. C. or AC. A related phrase, p. Chr. n., p. Ch. n., or post Christum natum complements a. Ch. n. and is equivalent to "Anno Domini".
In English, these phrases are rare and AC, ACN, and ante Christum natum are not in the Chicago Manual of Style, the American Heritage Dictionary, or P. Kenneth Seidelmann's Explanatory Supplement to the Astronomical Almanac.
The Anglo-Saxon historian Saint Bede used the Latin phrase ante incarnationis dominicae tempus in his Historia ecclesiastica gentis Anglorum of AD 731, and thereby became the first author to describe a year as being before Christ. Both Dionysius Exiguus and Saint Bede, who was familiar with the work of the former, regarded Anno Domini 1 as beginning on the date of the Incarnation of Jesus Christ, yet "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".