How do you write dates in Latin?

Question

I have read a little about the history of the Julian and Gregorian calendars. Julius Caesar introduced the twelve-month Julian calendar in 46 BC, and Pope Gregory XIII introduced the Gregorian calendar (a slight refinement of the Julian calendar) in the 16th century. However, this still leaves room for a lot of questions.

The first question is, when Pope Gregory introduced the Gregorian calendar, did he change the names of any months, or did he keep the exact same Latin names? I would like to use the Latin names for months, but the only names I can find are those belonging to the Julian calendar. It's probably safe to use these names, but I do want to make sure.

The second question is a little more interesting. I would like to say, in Latin,

Today is November 4, 2016

(or, to be more expansive) Today is the 4th of November of the year 2016

How would the Romans have said this during the late Roman republic (or the early empire)? Even though the Gregorian calendar replaced the Julian calendar, did the manner of stating the date in Latin change over all these centuries? Did they have a concise shorthand (like my first example) or were they more expansive (like the second)?

As a parting observation, I would like to point out that, in English, today is both a noun and an adverb, and that in my two examples above I am using the noun. In Latin, is there also a noun meaning today? If so, is this in common use, or is it more customary to use the adverb, hodie? Assuming the latter is true, I'm guessing that any declaration of the date would start with:

Hodie est...

But as for the rest, I'm at a loss. Many thanks for any feedback.

Answer 1

I will split this answer in two halves, for two different kinds of date expression.

On November 4

The traditional Roman calendar, whose system is still in use in some festive occasions, is based on three special days in each month: Kalendae (first day of the month), Nonae (fifth or seventh), and Idus (13th or 15th). The later options (7 and 15 instead of 5 and 13) were used in March, May, July, and October; in the other months Nonae was fifth and Idus thirteenth. All these three words are plural feminines.

The name Nonae should not be confused with the feminine plural of "ninth" (nonae). Capitalization and inflection both hint which one is meant, as feminine adjectives are not needed for dates. There are "ninth" days in the Roman calendar, but they occur in connection with Kalendae, never together with Nonae.

If the date falls on one of these special days, you simply put it in ablative:

• on March 1 = Kalendis Martiis
• on August 5 = Nonis Augustis
• on October 15 = Idibus Octobribus

In case of days immediately before special days, use the word pridies in ablative and put the special day in accusative. The name of the month is that of the special day, not necessarily that of the day of interest.

• on February 28 (29 on leap years) = pridie Kalendas Martias

(I have sometimes seen postridie used the same way for days right after a special day. If this method is used, then "on August 6" = postridie Nonas Augustas.)

For all other days, you count days to the following special day. As is typical in Latin, counting is inclusive:

• on October 13 = ante diem tertium Idus Octobres
• on October 12 = ante diem quartum Idus Octobres
• on October 17 = ante diem sextum decimum Kalendas Novembres

All these can be abbreviated, of course:

• Kal. Nov.
• prid. Id. Aug.
• a. d. XIV Kal. Dec.

Counting days before Kalendae Martiae on a leap year is a bit tricky, and I will exclude it here. This special case and the story behind it should be taken to a separate question.

In contemporary Latin, it is common to write things in a more simple and modern way: "on January 5" is simply die quinto mensis Ianuarii.

This can be abbreviated further without much risk of confusion. The first option I propose is to leave out die and mensis, since they can be understood implicitly, leaving us with quinto Ianuarii. Another option is to take the month name (which is an adjective in Latin) to modify the numeral or the implicit dies, leading to quinto Ianuario.

A year can be added by the ablative of annus and an ordinal numeral: Hic situs palam factus est Idibus Martiis anno bis millesimo sexto decimo.

Today is November 4

In the ancient literature phrases like "today is November 4" are rare but
Sebastian Koppehel found an example: Nonae sunt hodie Sextiles (Cic. Verr. 1, 10).

The word pridie is often considered an adverb since the noun pridies is only found in the singular ablative form used in dates. The leap to treating it as an actual noun is not huge and makes for more sensible and flexible date expressions, so we take it. Thus the old system can be adapted to such expressions:

• today is August 5 = hodie sunt Nonae Augustae
• today is March 31 = hodie est pridies Kalendas Apriles
• today is October 12 = hodie est dies quartus ante Idus Octobres

I stress that these are not all attested (as far as I know), but I consider them to be a reasonable extension of classical Latin. Notice that hodie is here an adverb, not the subject in the above sentences. If you want to emphasize this grammatical status in English, you may prefer to use "today it is…" instead of "today is…", but the meaning is of course the same.

Using the more modern variants, the construction is simple: "today is August 5" = hodie est dies quintus mensis Augusti. Again, ellipsis is possible if this feels too verbose.

A year can be added like in the "on November 4" case. But now genitive is more appropriate than ablative: "Today is December 6 of the year 1917." = Hodie est dies octavus ante Idus Decembres anni millesimi nongentesimi septimi decimi.

Conclusion

Let me end with listing all the possibilities I offer for November 4.

On November 4:

• pridie Nonas Novembres (prid. Non. Nov.)
• die quarto mensis Novembris (die 4 mensis Nov.)
• quarto Novembris (4 Nov.)
• [die] quarto Novembri (4 Nov.)

Today is November 4:

• hodie est pridies Nonas Novembres
• hodie est dies quartus mensis Novembris
• hodie est quartus Novembris
• hodie est [dies] quartus November

Answer 2

For the sake of completeness, I have seen lots of Ecclesiastical Latin dates written in the form: [die] roman numeral day (from I to XXXI)/[mensis] month in genitive/[anni] roman numeral year.

Just to cite two official examples (one recent, one more than 100 years old):

Datum Romae apud S. Petrum die XV Maii An. MDCCCXCI, Pontificatus Nostri Decimoquarto (Enc. Rerum Novarum)

 

Other example: Ex Aedibus Vaticanis/Die XXI mensis Novembris MMXII