In some contexts it is important to express whether a given date (for example October 25 and November 7 in 1917) is according to the Julian or the Gregorian calendar. Are there established Latin phrases for this? For example, should I say Nonis Aprilibus anno MCMX ad calendarium Iulianum/Gregorianum? Latin was in wider use when both calendars were used at the same time, so I assume there was an idiom for this purpose.

  • I've never come across this, and wonder if there was need enough for standard phrases? For what it's worth in interest, in English contemporary with the change the two systems were simply referred to by, for example, the historian of Rome Edward Gibbon, as 'O.S.' (Old Style, i.e. Julian) and 'N.S.' (New Style).
    – Tom Cotton
    Commented Aug 24, 2017 at 8:42

2 Answers 2


Google conjures up a good number of old books with "stylus (or stilus) vetus" and "stylus (stilus) novus".

  • It might be because Google personalizes search results, but I could not find a single hit for "stylus novus" used in a Latin text to refer to the choice of calendar. I found one hit for "stylus vetus". It is reasonable to expect that if these Latin phrases are used with German and some other languages, then it would be applicable in Latin as well. There were very few hits with stilus, too. Did you mean these Latin phrases used within other languages, or actual fully Latin documents using these phrases?
    – Joonas Ilmavirta
    Commented Aug 25, 2017 at 22:16
  • 2
    Here is an example in a Latin context. The author is a well-known astronomer, so someone who knows what he is talking about: books.google.co.uk/…
    – fdb
    Commented Aug 26, 2017 at 10:30
  • 1
    Thanks! For the benefit of those who cannot or do not want to follow the link, here is a telling passage: Notandum quod stylus vetus idem fit ac priscum Calendarium Julianum: sed stylus novus vel Gregorianus ante annum 1700. currentem, dies decem plus plusquam vetus numerabat...
    – Joonas Ilmavirta
    Commented Aug 26, 2017 at 13:05

Whatever it is that you intend to write, and if you need to make the distinction, it has obviously to be set at a time after the adoption of the Gregorian calendar. As I mentioned in a comment on the question, the two systems after the change were simply referred to as 'O.S.' (Old Style, i.e. Julian) and 'N.S.' (New Style) in English writings.

In adopting those references, a satisfactory word would be ratio, which I suggest is preferable to either modus or genus. I should myself choose any of these before stilus, although in classical times the word was sometimes actually used with a secondary meaning similar to that sought here — but that's just a personal preference. In the choice of adjectives there are various alternatives — for instance prior and vetus, recens,novus and perhaps infimus, none of which seems controversial — though one might just as comfortably (and more clearly) use Julianus and Gregorianus instead of 'old' and 'new'.

In a later context, in times when it has/had become customary to use simple ordinals for the days of the month in English, it's not really appropriate to use the method of expressing dates from classical times. By the time the Gregorian system had been adopted across Europe, if not earlier, the old Ides of March, for example, would generally be written in correspondence as something like dies XV mensis Martialis A.D.MDCCLXXVII.

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