Definition
Latin: "In the year of the Lord." The system of dating that counts years forward from the traditionally reckoned birth of Jesus Christ. Commonly abbreviated A.D. and placed before the year number (e.g., A.D. 1776), though modern usage often places the abbreviation after. Anno Domini is the formal designation for dates expressed in the Christian era and has been the dominant dating convention in Western legal documents for centuries.
In legal instruments — indictments, declarations, deeds, pleadings — a date expressed as "Anno Domini" or "A.D." situates the event or execution within this calendar system. The phrase is functionally equivalent to the secular alternative "CE" (Common Era) now preferred in some academic and international contexts, but legal documents in the Anglo-American tradition have historically used Anno Domini without controversy.
Common Language
Modern common usage (Wiktionary): "In the year of our Lord (often abbreviated A.D. or AD)."
Historical common usage (Webster's 1913): "In the year of the Christian era; as, a. d. 1887."
The gap between common and legal meaning here is minimal in substance but significant in procedural consequence. In ordinary usage, "Anno Domini" is simply a date marker. In legal usage, its appearance in a pleading or indictment raised a formal question: whether a Latin phrase in an otherwise English-language document rendered the instrument defective. Courts resolved this by treating "Anno Domini" as fully Anglicized — absorbed into common legal English — so that its presence does not expose a pleading to demurrer on language grounds.
Common Confusion
Anno Domini is sometimes conflated with the abbreviation B.C. ("Before Christ") or the secular alternatives BCE/CE. These are not interchangeable systems — they anchor to the same epochal reference point but run in opposite directions from it. Researchers reading historical documents should also be alert to the Old Style / New Style calendar distinction: before the adoption of the Gregorian calendar in England in 1752, dates expressed as Anno Domini in English legal instruments followed the Julian calendar, and the legal new year began on March 25 (Lady Day), not January 1. A document dated "February 10, A.D. 1700" in an English court record may correspond to what we would call February 10, 1701 under the modern calendar.
Why It Matters in Research
The primary research value of this entry is navigational and cautionary rather than definitional. Three issues arise in corpus work:
First, dating ambiguity in pre-1752 English and colonial American records. Documents using Anno Domini before the Gregorian calendar reform require double-date conversion for the January 1 – March 24 window each year. A legal instrument executed in "February A.D. 1700" under Old Style reckoning is February 1701 by modern reckoning. Failure to account for this produces sequencing errors in chronological research.
Second, the Anglicization doctrine. The 2nd edition of Black's cites authority for the proposition that "Anno Domini" in a pleading does not make the pleading Latin — or non-English — for purposes of procedural objection. Researchers examining early American and English pleading practice should be aware that this was a live question, not merely academic. Demurrers on this ground were attempted.
Third, abbreviation variation in historical sources. Legal documents use A.D., AD, Anno Dom., Anno Domini, and occasionally the spelled-out Latin in full. Corpus searches should account for all variants, particularly in document metadata and transcriptions where abbreviation expansion is inconsistent.
Historical Dictionary Support
Both editions of Black's offer the same core definition — "In the year of the Lord," computation of time according to the Christian era from the birth of Christ — but the 2nd edition adds the procedurally important gloss that Anno Domini has become Anglicized by adoption. This is not a trivial addition. It reflects actual litigation history: the phrase appeared in English-language pleadings and was challenged on the theory that Latin terms rendered documents non-compliant with requirements that legal proceedings be conducted in English. Courts rejected this, treating Anno Domini as having passed into legal English by long custom.
The historical dictionaries do not address the Old Style / New Style calendar issue, the BCE/CE distinction, or the dating complexities that arise in colonial records — all of which are practically significant for researchers working with historical legal documents. Black's treatment is accurate but thin relative to what a corpus researcher needs.
Jurisdictional Note
The Anglicization doctrine — that Anno Domini in a pleading is not demurrable as a Latin intrusion — was established in early American and English courts and is not a live controversy in any modern jurisdiction. The dating convention itself is universal in Anglo-American legal documents, though international instruments increasingly use the secular CE designation alongside or instead of A.D.