A.D. - Anno Domini, the year of our Lord

Anno is latin for year.
Domini is latin for Lord.
Therefore, Anno Domini means the year of our Lord.

Of course, if you trace back 2015 years you will note that it starts with the birth of Jesus Christ, thus "our Lord" is The Lord Jesus Christ.

Anno Domini is a shortened version of Anno Domini Nostri Iesu Christi

So today's date would most accurately be proclaimed as March 29, in the Year of our Lord Jesus Christ 2015.

Jesus Christ is the same yesterday and today and forever.
Hebrews 13:8


1. http://www.theopedia.com/Anno_Domini