I've encountered the abbreviation: 'Ad.' used in an old (early 20th century?) hand-written family tree am quite ignorant of its meaning. It's used in conjunction with a specific date, e.g. 'Thomas Chaplin Born about 1703, Ad. 2nd March 1725' or 'John Chaplin Ad. Jany 27th 1730' and all such Ad. dates (for 25 people across 5 successive generations)are before 1837/1841. The entry for one Robert C, whose exact birth, marriage and death dates are documented has an Ad. date 7 years prior to his marriage, when he would have been 22 years old.

Is anyone able to help me please? There may be a simple answer, but it would help me enormously to know what this means.