I had to wake up before 3 am this morning (on a Sunday!), and I had to worry about the start of daylight saving time. (It always starts on the last Sunday of March in Europe. Other areas have other conventions.) This left me wondering, among other things, about expressing times when DST ends.

When the last Sunday of October comes and clocks are turned back one hour at 4 am in Finland, how can I refer to the times from 3 to 4 am that occur twice? It would be great if there is a canonical expression, but I am open to any suggestions.

I have two ideas for distinguishing the two instances of 4 am:

  • hora quarta and hora bis quarta (by analogy to the second instance of a day on leap years marked by bis)
  • hora quarta temporis aestivi/hiemalis

The second one is unambiguous but feels a bit heavy. The first one sounds more idiomatic to me, but the plain hora quarta is ambiguous. Perhaps one could contrast the bis with a semel? How would you make the distinction in Latin and why?

I am using the modern convention where horae are counted from midnight and noon, not the Roman one. Whichever convention you prefer, the question remains: how to remove ambiguity?

I should add that although I ask only about Latin, I don't know a canonical pair of distinctive expressions in any language.

  • 1
    In Dutch, you can easily contrast "summer time" and "winter time" (or, where I'm from, people say "summer hour" and "winter hour"). Same thing in French, apparently: fr.wikipedia.org/wiki/Heure_d%27hiver So I would go for tempus aestivum/hiemale for more correctness and clarity, but I think I'd take semel/bis if I wanted to sound more idiomatic.
    – blagae
    Commented Mar 27, 2017 at 10:15

1 Answer 1


The question posted is analogous to the other one: how do you distinguish the sixth hour of the morning with the sixth hour of the afternoon? In English, two expressions in Latin are used: ante meridiem and post meridiem. So I don't see any difficulty in using the second form. If it's too long, abbreviate it, like we do with AM and PM... Although it might be good to write it out longhand in the first occurrence in a text with the initialism in brackets, and then just the initialism in subsequent uses, since it is definitely not standard in any sense of the word.

So: hora quarta tempore hiemali (TH) and hora quarta tempore aestivo (TA)

Alternatively, aestivus/hiemalis can qualify hora directly: hora quarta aestiva and hora quarta hiemali. I guess that could be considered "sufficiently" brief for everyday use.

Finally, I have managed to find out this excerpt of the Vatican-published Lexicon Recentis Latinitatis, which contains the term hora legitima as a translation of the Italian ora legale, which is used in that country to stand for the US "Daylight Saving Time." Whether this is better than hora aestiva/tempus aestivum is probably a matter of taste, but I feel that using hora legitima will cause anyone who's not an Italian to scratch their heads.

  • Good suggestion! I like the direct use of adjectives. (Minor note: wouldn't the ablative be hiemali?) I wouldn't use the abbreviations, though, since they are not (?) standard.
    – Joonas Ilmavirta
    Commented Mar 28, 2017 at 19:01
  • @JoonasIlmavirta: You're right, of course. 2nd Class Adjectives are I-stem. Fixed in the answer
    – Wtrmute
    Commented Mar 28, 2017 at 19:23

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