Definition
"Anno Domini" (often abbreviated as AD) is a Latin phrase meaning "in the year of the Lord." It's used to number years in the Julian and Gregorian calendars, referring to the supposed year of Jesus Christ's birth. Years are counted *after* that starting point. It contrasts with BC (Before Christ), which counts years *before* that point. Essentially, it's a way of dating historical events. AD is often used interchangeably with CE (Common Era).