Re: 24-hour vs. 12-hour time, ambiguity, and abbreviations (was Re: Default date output format changed after an upgrade to buster)
On Thu 12 Sep 2019 at 12:42:01 (-0400), The Wanderer wrote:
> On 2019-09-12 at 12:03, David Wright wrote:
> > On Thu 12 Sep 2019 at 09:42:03 (-0400), The Wanderer wrote:
> >> On 2019-09-12 at 06:30, Dan Ritter wrote:
>
> >>> There is only one sensible interpretation:
> >>>
> >>> If 11:59 AM is two minutes before 12:01 PM, then 12:00 is PM.
> >>>
> >>> If 11:59 PM is two minutes before 12:01 AM, then 12:00 is AM.
> >>
> >> I take a slightly different approach, based on the apparent actual
> >> meanings of the words for which "AM" and "PM are abbreviations.
> >>
> >> It seems intuitively obvious to me that between 11:59 Ante-Meridiem and
> >> 12:01 Post-Meridiem must lie 12:00 Meridiem. (Though 12:00:01 - one
> >> second later - would be Post-Meridiem again.)
> >>
> >> Similarly, though less an "obvious necessity" consequence, between 11:59
> >> Post-Meridiem and 12:01 Ante-Meridiem lies 12:00 Midnight. (I understand
> >> "meridiem" to be derived from a word which would have literally meant
> >> "mid-day".)
> >
> > Meridies (nominative case in Latin).
> >
> >> Both are intuitively represented as "12:00 M" - with no "A" or "P" - and
> >> that, in its turn, is ambiguous.
> >
> > It might be ambiguous if m were also an abbreviation for midnight,
> > which I've never come across.
>
> Neither have I, but I also haven't come across any *other* abbreviation
> for it which might be used in this type of context (have you?), and "M"
> is just as intuitive a choice for abbreviating "midnight" as it is for
> abbreviating "meridiem".
>
> One could argue "M" for "midnight" and "N" for "noon", but then you lose
> the intuitiveness of M for meridiem, and people would mishear the two as
> each other in nonline conversation all the time anyway.
I don't see a need for a one-letter abbreviation for midnight, nor the
wisdom in introducing one that's already used in the same context.
Where would you use it? Why not just drop 12-hour times? I don't think
I've ever formatted a 12-hour time on a computer (unless you want to
count the example quoted below).
Even accepting that 24:00 Thursday and 00:00 Friday express the same
time could be risky unless you know and trust that the source is
consistent. That's why people like insurance companies often use 23:59
and 00:01, because to them the exact day matters.
> >> That being part of why I stick with 24-hour time whenever possible.
> >
> > When I read emails, I only see the Date: line from the header, and
> > the timedates used in the quotation lines. One thing I find odd is
> > mixing AM/PM with hours containing a leading zero. I was always
> > taught that 7 p.m. or 7pm was not written as 07, but I see that a
> > lot here. Contrast
> >
> > $ TZ=Europe/Paris date +'%I.%M %p'
> > 06.01 PM
> > $ TZ=Europe/Paris date +'%l.%M %p'
> > 6.01 PM
> > $
>
> That's probably to ease parsing by automated tools, such as sort, so
> that they don't have to worry about handling field width.
That wouldn't be possible anyway, because you don't have control over,
for example, whether the time follows the date, and other variability.
No. I think it's more likely that most people don't notice conventions
unless they're brought to their attention. Of course, if you're old
enough, you had years of pre-digital experience when no one thought of
padding dates and times with 0s. That might be why I notice 'odd'
formatting like this.
Cheers,
David.
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