When is midnight? Nomenclature question

Paul Eggert eggert at CS.UCLA.EDU
Mon Apr 24 06:31:11 UTC 2006

Ken Pizzini <tz. at explicate.org> writes:

> On Sun, Apr 23, 2006 at 12:14:36AM -0700, Paul Eggert wrote:
>> I once had a
>> printed airline ticket that said I left LAX at "1200N", meaning noon.
> Even worse, I've seen legislative hearings that were scheduled for
> "12:00 M".  The "M" here means... no, not midnight, but meridian ---
> i.e., noon!

Yes, that is a dreadful ambiguity.  I hope US airlines don't use
"1200M" for midnight, though, as that would be ambiguous as to date.

A Latin-language nit, though: "M" means "meridies", not "meridian".

"Meridies" was an irregularly formed Latin word: it meant "midday" and
came from "medius" mid + "dies" day, which were originally combined
into "medidies", but the Romans eventually changed the first D to an R.

  Postea quinta littera sublata, et subrogata r dicta est laurus, ut
  in auriculis que in inicio audicule dicte sunt, et medidies qui nunc
  meridies dicitur.

  ("Later the letter D was removed and replaced by R, so that it was
  called laurus, as in the words auricule, which was originally
  audicule, and medidies, now called meridies.")

  -- Aberdeen Bestiary entry for "laurel" (circa 1200)

This just goes to show you that the problem with what exactly to call
"noon" and "midnight" goes back _millennia_.

I agree with Markus Kuhn that "00:00", "12:00", and (let's hope
rarely) "24:00" are the best ways to attack the problem nowadays.

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