Adam Borowski:
...
> The latter have weird customs like a medieval system of measurements, units
> that differ on dry-vs-liquid-vs-slightly-moist, or different distances by
> the same name on air vs land vs survey measurements.

Just go back 50-60years and you'll find that we used a lots of different
"thumb" and other units here also. And it's usage is still lingering although
diminishing. Sometimes it is used as an indication of a person who
"knows" his trade, like 5" nail instead of 125mm nail.

And regarding your last comment, here in Sweden we still use mil (=10km)
and distansminut (=1852m, nautical mile) as a complement to the boring km.

Doesn't the airplane etc. people all arond the globe talk about flying
heights in feet.

And annoyingly many persons excels in using mils (=1/1000 inch) instead
of mm in the pcb industry even though components with pitch derived from
inch grids are quickly becoming obsolete.

Yea, thoose "medieval" units still has a somewhat strong hold on us all.

...
> And, also, a discontinuous system of time with four non-monotonic segments
> and ambiguous endpoints; marked with "am" and "pm".
...

Isn't it so that all (?) analogue clocks show 0-12 and you must infer
the "am" and "pm" part from context. And in informal situations you
(at least here) say five a'clock, not 17:00. The difference is we use
a 24h clock in formal situations or when we want to be more specific.

///

Upstream date (coreutils) has got a debug flag that might be useful:

$ LC_TIME=sv_SE ./date --debug
./date: output format: ?%a %e %b %Y %H:%M:%S %Z?
tis 30 mar 2021 18:39:34 UTC
$ LC_TIME=en_US ./date --debug
./date: output format: ?%a %d %b %Y %r %Z?
Tue 30 Mar 2021 06:39:38 PM UTC

Regards,
/Karl Hammar