Years were given in one of two ways: either with reference to the year's consuls, or with reference to the year of the founding of the City.
When using Consular dating the names of both consuls were given in the ablative case, followed by the word "consulibus (cos.)." So, 63 BCE would be "M. Tullio Cicerone C. Antonio Hibrida consulibus" ("M. Tullius Cicero and C. Antonius Hibrida being the consules"). Also, it was not uncommon to shorten this to "M. Tullio C. Antonio cos." or even "Cicerone Hibridaque cos."
N.B. The consular date is not the name of the year but a description of the year, meaning "X and Y being consules" or "while X and Y were consules". So one does not say "the conspiracy of Catilina was thwarted in M. Tullio C. Antonio cos." but simply "the conspiracy of Catilina was thwarted M. Tullio C. Antonio cos."
Dating from the founding of the city
When using reference to the founding of the City (i.e., Rome), the accepted date is 753 BCE, which would make the year 2001, for instance, "2754." This number is given, followed by the words "anno Urbis conditae" or "ab Urbe condita" ("in the year of the founding of the City" or "from the City being Founded"), both abbreviated "a.u.c."
The pre-Julian Latin name and forms are only given when in disagreement with the Gregorian equivalents.
Kalends, Nones, and Ides
The Kalends ("Kalendae", in Latin; abbr. "Kal.") always fall on the first day of the month. The Nones (Nonae, "Non.") fall mostly on the 5th, but on the 7th in March, May, July, and October. The Ides (Idus, "Id.") fall mostly on the 13th, but on the 15th in those months just mentioned.
When the date to be given is one of these three sacred days (Kalends, Nones, Ides), the date is given as the day and month, both in the feminine ablative plural. Therefore, "Kalendis Aprilibus," "Nonis Septembribus," "Idibus Maiis."
Dates were given by counting, inclusively, backwards from the next reference day, putting this number, ordinally, in the accusative case, after the words "ante diem," excepting one case, which is the day before the referenced day, in which case rather than the number and "ante diem," the word "pridie" was used instead. Usually, instead of writing each word out, the words "ante diem" were abbreviated to "a.d.," "pridie" is abbreviated to "pr.," and the number was just given as a numeral. Following this, the referenced sacred day and month was placed in the feminine accusative plural.
To refer to the 29th of January, for instance, the date would be "ante diem quartum Kalendas Februarias (a.d. IV Kal. Feb.)," literally translated to "the fourth day before the February Kalends (usually reckoned as "Kalends of 'month'"). Similarly, the 14th of March: "pridie Idus Martias (pr. Id. Mar.)," i.e., "the day before the March Ides."
Table of Dates
|2||a.d. IV Non.||a.d. IV Non.||a.d. VI Non.||a.d. IV Non.|
|3||a.d. III Non.||a.d. III Non.||a.d. V Non.||a.d. III Non.|
|4||pridie Nonas||pridie Nonas||a.d. IV Non.||pridie Nonas|
|5||Nonis||Nonis||a.d. III Non.||Nonis|
|6||a.d. VIII Id.||a.d. VIII Id.||Pridie Nonas||a.d. VIII Id.|
|7||a.d. VII Id.||a.d. VII Id.||Nonis||a.d. VII Id.|
|8||a.d. VI Id.||a.d. VI Id.||a.d. VIII Id.||a.d. VI Id.|
|9||a.d. V Id.||a.d. V Id.||a.d. VII Id.||a.d. V Id.|
|10||a.d. IV Id.||a.d. IV Id.||a.d. VI Id.||a.d. IV Id.|
|11||a.d. III Id.||a.d. III Id.||a.d. V Id.||a.d. III Id.|
|12||pridie Idus||pridie Idus||a.d. IV Id.||pridie Idus|
|13||Idibus||Idibus||a.d. III Id.||Idibus|
|14||a.d. XIX Kal.||a.d. XVI Kal.||pridie Idus||a.d. XVIII Kal.|
|15||a.d. XVIII Kal.||a.d. XV Kal.||Idibus||a.d. XVII Kal.|
|16||a.d. XVII Kal.||a.d. XIV Kal.||a.d. XVII Kal.||a.d. XVI Kal.|
|17||a.d. XVI Kal.||a.d. XIII Kal.||a.d. XVI Kal.||a.d. XV Kal.|
|18||a.d. XV Kal.||a.d. XII Kal.||a.d. XV Kal.||a.d. XIV Kal.|
|19||a.d. XIV Kal.||a.d. XI Kal.||a.d. XIV Kal.||a.d. XIII Kal.|
|20||a.d. XIII Kal.||a.d. X Kal.||a.d. XIII Kal.||a.d. XII Kal.|
|21||a.d. XII Kal.||a.d. IX Kal.||a.d. XII Kal.||a.d. XI Kal.|
|22||a.d. XI Kal.||a.d. VIII Kal.||a.d. XI Kal.||a.d. X Kal.|
|23||a.d. X Kal.||a.d. VII Kal.||a.d. X Kal.||a.d. IX Kal.|
|24||a.d. IX Kal.||a.d. VI kal||a.d. bis VI Kal.||a.d. IX Kal.||a.d. VIII Kal.|
|25||a.d. VIII Kal.||a.d. V Kal.||a.d. VI Kal.||a.d. VIII Kal.||a.d. VII Kal.|
|26||a.d. VII Kal.||a.d. IV Kal.||a.d. V Kal.||a.d. VII Kal.||a.d. VI Kal.|
|27||a.d. VI Kal.||a.d. III Kal.||a.d. IV Kal.||a.d. VI Kal.||a.d. V Kal.|
|28||a.d. V Kal.||pridie Kalendas||a.d. III Kal.||a.d. V Kal.||a.d. IV Kal.|
|29||a.d. IV Kal.||(-)||pridie Kalendas||a.d. IV Kal.||a.d. III Kal.|
|30||a.d. III Kal.||(-)||(-)||a.d. III Kal.||pridie Kalendas|
|31||pridie Kalendas||(-)||(-)||pridie Kalendas||(-)|