Alternative spellings

Various authorities support the different styles:

• anno domini
• anno Domini

Adverb

Anno Domini

1. In the year of our Lord (often abbreviated A.D. or AD).
   • 1620 — Mayflower Compact

     In Witness whereof we have hereunto subscribed our names at Cape Cod the eleventh of November, in the Reign of our Sovereign Lord, King James of England, France and Ireland, the eighteenth, and of Scotland the fifty-fourth. Anno Domini, 1620.

   • 1859 — Charles Dickens, A Tale of Two Cities

     The scene was Mr. Cruncher’s private lodging in Hanging-sword-alley, Whitefriars: the time, half-past seven of the clock on a windy March morning, Anno Domini seventeen hundred and eighty.

Anno Domini (abbreviated as AD or A.D., sometimes found in the irregular form Anno Domine) and Before Christ (abbreviated as BC or B.C.) are designations used to label years in the Julian and Gregorian calendars. The calendar era to which they refer is based on the traditionally reckoned year of the conception or birth of Jesus, with AD denoting years after the start of this epoch, and BC denoting years before the start of this epoch. There is no year zero in this scheme, so the year AD 1 immediately follows the year 1 BC.

The Gregorian calendar, and the year numbering system associated with it, is the calendar system with the most widespread use in the world today. For decades, it has been the unofficial global standard, recognized by international institutions such as the United Nations and the Universal Postal Union. It is also a basis of scholarly dating, though some people adopt the Common/Christian Era labels, retaining the same numeric values but using the label "CE" (Common/Christian Era) instead of "AD", and "BCE" (Before the Common/Christian Era) instead of "BC".

The term Anno Domini is Medieval Latin, translated as In the year of (the/Our) Lord. It is sometimes specified more fully as Anno Domini Nostri Iesu (Jesu) Christi ("In the Year of Our Lord Jesus Christ").

Traditionally, English has copied Latin usage by placing the abbreviation before the year number for AD; since BC is not derived from Latin it is placed after the year number (for example: 68 BC, but AD 2010). However, placing the AD after the year number (as in "2010 AD") is now also common. The abbreviation is also widely used after the number of a century or millennium, as in "fourth century AD" or "second millennium AD" (although conservative usage formerly rejected such expressions).

Because BC is the English abbreviation for Before Christ, it is sometimes incorrectly concluded that AD means After Death, i.e., after the death of Jesus. If that were true, the thirty-three or so years of his life would not be in any era.