Anno Domini (AD or A.D.) and Before Christ (BC or B.C.) are designations used to label or number years used with the Julian andGregorian calendars. The term Anno Domini is Medieval Latin, translated as In the year of the Lord, or in the Year of Our Lord. It is occasionally set out more fully as Anno Domini Nostri Iesu Christi. This calendar era is based on the traditionally reckoned year of the conception or birth of Jesus of Nazareth, with 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, so the year AD 1 immediately follows the year 1 BC. This dating system was devised in 525, but was not widely used until after 800.