Bug 497514

SUMMARY

AM/PM is not localized to my locale setting (LC_TIME=el_GR.UTF-8). See below in steps to reproduce for examples.

Moreover, while attempting to workaround this I came across the following issues:
1. Digital Clock allows one to configure the date format, but not the time format (the field is called "Date format", but the link below it has a label of "Time Format documentation", which is a bit jarring by itself). Putting "h:mm ap" or "hh:mm AP" in there manually results in the correct, localized AM/PM setting which could serve as a workaround. However, it's not possible to hide the default time format from the widget.
2. Setting the clock to a 24-hour format, as another attempt to  attempt to mask the AM/PM issue, is setting the clock to e.g. "9:45" instead of "09:45", which is quite confusing, at least in my locale. Again, one can configure "date format" to "HH:mm", but cannot hide the default clock formatting.

STEPS TO REPRODUCE
1. Set locale to el_GR.UTF-8. In my case: LANG=el_GR.UTF-8 LANGUAGE=en_US:en LC_MESSAGES=en_US.UTF-8.
2. Set date format to "Long date".
2. Set digital clock to 12-Hour mode.
3. Observe the clock.
4. Set date format to "Custom". Set date format to "dddd MMMM d hh:mm ap", to demo that the time is localized when formatted manually, but not when formatted automatically.
5. Observe the clock.

OBSERVED RESULT
After step 3: Κυριακή 15 Δεκεμβρίου 2024 7:07 PM
After step 5: Κυριακή 15 Δεκεμβρίου 2024 7:07 μ.μ. 7:07 PM

EXPECTED RESULT
After step 3: Κυριακή 15 Δεκεμβρίου 2024 7:07 μ.μ.
After step 5: Κυριακή 15 Δεκεμβρίου 2024 7:07 μ.μ. 7:07 μ.μ.

SOFTWARE/OS VERSIONS
Operating System: Debian GNU/Linux 12
KDE Plasma Version: 6.2.4
KDE Frameworks Version: 6.8.0
Qt Version: 6.7.2
Kernel Version: 6.12.3-amd64 (64-bit)

ADDITIONAL INFORMATION

Note that I have a slightly unusual setup with LANG=el_GR.UTF-8 LANGUAGE=en_US:en LC_MESSAGES=en_US.UTF-8 on a Debian unstable system. However, I've verified that this happens on a live VM with KDE Neon, when changing language from system settings to Greek, and logging out/in again.

Also note that in my locale, the normal case for AM/PM is lowercase, i.e. "π.μ./μ.μ". Qt calls this "ap", I believe, in constrast to "AP". The Plasma widget code seems to hardcode "AP" as far as I can tell, so I'm noting this in case it matters when fixing the broader localization issue.

On a yet another unrelated issue, on my Debian unstable desktop, with Plasma 6.2.4, systemsettings under Region & Language -> Time, the time is formatted as "Π.Μ./Μ.Μ (uppercase), but in KDE Neon as "π.μ./μ.μ." (lowercase). This is probably not a plasmashell issue, but I have no idea where it lies or how to report it...