There has been a wrong conception that AD is an acronym for "After Death". This is untrue, AD means Anno Domini (AD or A.D.) which can be literally translated to "In the year of our Lord"

AD (The year of our Lord) therefore commenced in the year Jesus was born and not in the year he died.

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 and Gregorian calendars. The term Anno Domini is Medieval Latin, translated as In the year of the Lord,[1] or in the Year of Our Lord.[2][3]:782 It is occasionally set out more fully as Anno Domini Nostri Iesu (or Jesu) Christi ("In the Year of Our Lord Jesus Christ". 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.[4]

The Gregorian calendar is the most widely used calendar in the world today. For decades, it has been the unofficial global standard, adopted in the pragmatic interests of international communication, transportation, and commercial integration, and recognized by international institutions such as the United Nations and the Universal Postal Union.[5][self-published source]

Traditionally, English followed Latin usage by placing the "AD" abbreviation before the year number.[6] But BC is placed after the year number (for example: AD 2015, but 68 BC), which also preserves syntactic order. 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).[7] 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. However, this would mean that the ~33 years commonly associated with the life of Jesus would not be included in either BC or AD time scales.[8]

Terminology that is viewed by some as being more neutral and inclusive of non-Christian people is to call this the Current, or Common Era (abbreviated as CE or C.E.), with the preceding years referred to as Before the Common, Christian, or Current Era (BCE or B.C.E.). Astronomical year numbering and ISO 8601 avoid words or abbreviations related to Christianity, but use the same numbers for years AD.

SOURCE : http://en.wikipedia.org/wiki/Anno_Domini