A Latin date counts backwards from one of three anchor days: the Kalends (the 1st of the month), the Nones (the 5th — or the 7th in March, May, July and October), and the Ides (the 13th — or the 15th in those same four months). Kalendis Ianuariis is 1 January; pridie Idus Martias is 14 March. The count is inclusive: the anchor day itself is day one.
The three anchor days
Roman months do not number their days forward. They count backwards from three fixed points:
| Anchor | Latin (nom. pl.) | Most months | March, May, July, October |
|---|---|---|---|
| Kalends | Kalendae | 1st | 1st |
| Nones | Nonae | 5th | 7th |
| Ides | Idus | 13th | 15th |
The Ides of March — the day of Caesar's assassination in 44 BC — is the 15th, not the 13th, because March is one of the four long months.
How to read a Roman date
Three forms cover nearly every date on a diploma.
On the anchor day itself — ablative absolute, no counting:
- Idibus Martiis — "on the Ides of March" = 15 March
- Kalendis Ianuariis — "on the Kalends of January" = 1 January
Before the anchor day — ante diem + ordinal + accusative, counted inclusively:
- ante diem tertium Kalendas Novembres (a.d. III Kal. Nov.) — "the third day before the Kalends of November" = 30 October. The count includes both ends: 1 November is day one, 31 October is day two, 30 October is day three.
- ante diem sextum Idus Iulias (a.d. VI Id. Iul.) — "the sixth day before the Ides of July" = 10 July. The Ides of July fall on the 15th; counting back inclusively — 15, 14, 13, 12, 11, 10 — the sixth day is the 10th.
The day before the anchor — pridie + accusative:
- pridie Idus Martias — 14 March
- pridie Kalendas Ianuarias — 31 December
A Roman leap year did not append a day at the end of the month the way our 29 February does — it repeated one already in it. The sixth day before the Kalends of March (24 February) simply came twice: ante diem bis sextum Kalendas Martias, the origin of the word bissextile.
The month names in dating formulas
On classical-formula diplomas the month appears as an adjective agreeing with the anchor (Kalendae Martiae, Nonae Iuliae, Idus Octobres). On modern simplified formulas it appears as a genitive after mensis, "month":
| Month | With anchor (abl. pl.) | After mensis (gen.) |
|---|---|---|
| January | Ianuariis | Ianuarii |
| February | Februariis | Februarii |
| March | Martiis | Martii |
| April | Aprilibus | Aprilis |
| May | Maiis | Maii |
| June | Iuniis | Iunii |
| July | Iuliis | Iulii |
| August | Augustis | Augusti |
| September | Septembribus | Septembris |
| October | Octobribus | Octobris |
| November | Novembribus | Novembris |
| December | Decembribus | Decembris |
Note the split: six months decline as ordinary adjectives (Ianuariis, Maiis, Iuliis), while the other five are third-declension i-stems and take -ibus (Aprilibus, Septembribus).
The year
Diplomas write the year in Roman numerals, normally with anno Domini or a local equivalent:
- anno Domini MMXXIV — in the year of the Lord 2024
- Datis Annandale A.D. — a locative dateline ("given at Annandale") whose final letters are not Anno Domini at all; one of the standing traps on American diplomas
Older documents may omit anno Domini, date by an indiction cycle — the fifteen-year convention of the papal chancery — or, in ecclesiastical documents, by feast day ("the Monday next after the feast of the Lord's Ascension"). Each of these is handled by identification on the certified translation, not by guesswork.
What real diplomas do
Two formula families cover nearly all university diplomas.
Classical: Datum [place] Kalendis Ianuariis anno Domini MMXXIV — "Given at [place], on the Kalends of January, in the year of the Lord 2024."
Modern simplified: Die decimaquarta mensis Martii anno Domini MMXXIV — "On the fourteenth day of the month of March, in the year of the Lord 2024." The ordinal is spelled out, and the month stands in the genitive after mensis.
Both are rendered as an unambiguous modern date on the certified translation, with the original Latin formula preserved in the layout — which is what registrars and evaluators check against the conferral record.
Why machine translation gets these dates wrong
- Kalendis is treated as an untranslated proper name, so the date vanishes from the output entirely.
- The inclusive count is dropped: "the third day before the Kalends" comes out as the 28th instead of the 30th.
- Pridie is silently omitted, shifting every date it touches by one day.
- The four long months — March, May, July, October — are treated like the rest, moving every Nones and Ides by two days.
- a.d. is expanded as Anno Domini, the far commoner expansion, producing a date that is not approximately wrong but structurally impossible.
A certified translation states the converted date explicitly and keeps the original formula visible beside it. On a diploma, that is the difference between a document that matches the registrar's record and one that does not.
Frequently asked questions
How do you read a Latin date on a diploma?
Find the anchor — Kalends, Nones, or Ides — then count backwards inclusively if ante diem appears, or subtract one day for pridie. The anchor day itself is given in the ablative, with no counting at all.
What are Kalends, Nones and Ides?
The three anchor days of the Roman month: the Kalends are the 1st; the Nones are the 5th, or the 7th in March, May, July and October; the Ides are the 13th, or the 15th in those four months.
Is the Ides of March the 13th or the 15th?
The 15th. March is one of the four months whose Nones and Ides fall on the later dates — the 7th and the 15th — along with May, July and October.
How is a Latin date written on a certified translation?
As an unambiguous modern date — for example, "15 March 2024" — with the original Latin formula preserved in the document layout alongside it, so the receiving registrar or evaluator can check it against the conferral record.
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