BC = Before Christ
AD = Anno Domini = In the year of the LORD
Anno Domini nostri Jesu Christi = In the year of our Lord Jesus Christ
“The terms anno Domini (AD) and before Christ (BC)[note 1] are used to label or number years in the Julian and Gregorian calendars. The term anno Domini 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“.