AD
From TARDIS Index File, the free Doctor Who reference.
A.D. is the abbreviated form of Anno Domini (Latin for "Year of the Lord"), and commonly used in the English-speaking world. The AD epoch begins with the year traditionally designated as that of the birth of Jesus Christ. Adric refers to this dating method when he informs Tegan that the TARDIS had arrived in the year, "2526 in the time scale you call Anno Domini." (DW: Earthshock)
