Anno Domini

The terms (AD) and before Christ (BC)}} are used when designating years in the Julian and Gregorian calendars. The term is Medieval Latin and means "in the year of the Lord" but is often presented using "our Lord" instead of "the Lord", taken from the full original phrase "''anno Domini nostri Jesu Christi''", which translates to "in the year of our Lord Jesus Christ". The form "BC" is specific to English, and equivalent abbreviations are used in other languages: the Latin form, rarely used in English, is (ACN) or (AC).

This calendar era is based on the traditionally reckoned year of the conception or birth of Jesus, ''AD'' counting years from the start of this epoch and ''BC'' denoting years before the start of the era. There is no year zero in this scheme; thus the year AD 1 immediately follows the year 1 BC. This dating system was devised in 525 by Dionysius Exiguus but was not widely used until the 9th century.

Terminology that is viewed by some as being more neutral and inclusive of non-Christian people is to call this the Common Era (abbreviated as CE), with the preceding years referred to as Before the Common Era (BCE). Astronomical year numbering and ISO 8601 avoid words or abbreviations related to Christianity, but use the same numbers for AD years (but not for BC years in the case of astronomical years; e.g., 1 BC is year 0, 45 BC is year −44). Provided by Wikipedia