Comment 1 for bug 47702

Well, you're mistaken that 12-hour format is just en_US - for one thing, it's what the locale files for en_GB say too (see /usr/share/i18n/locales/en_GB and search for "am_pm"). We do try to use the chosen locale. However, it doesn't seem to quite work properly in the case where different countries within the same language have different LC_TIME conventions, and it won't work properly for countries whose locale definitions haven't been generated. Hmm. This may be complicated to fix.