Thunderbird does not seem to respect locale for datetime

[equaeghe]

(I have asked this question on the Thunderbird support forums, but did not yet get any pointers that might help me.)

I use Thunderbird 128.6.0. I have set it to use my regional settings (i.e., locale). Namely intl.regional_prefs.use_os_locales=true. That meant, because I have set LC_TIME="nl_NL.UTF-8" (and in Thunderbirds config I can see that it picks up "Nederlands (Nederland)" as it should), that time was in 24-hour format (in the date column of the message list and in the message header). Recently, it switched to a 12-hour a.m./p.m. format (e.g., 07-01-2025 1:47 p.m. instead of something with 13:47). How do I get it to use a 24-hour format again?

I do not want to fiddle with Thunderbird datetime formatting settings (I have none of the intl.date_time.pattern_override options set.). I just want my locale settings to be used. If it turns out locale settings have changed, I need to fix those. (I do not think so, on the command line, the `date` command returns "do 9 jan 2025 19:33:33 CET", something in 24-hour format.) Namely: