Users in a given locale have different requirements for date-time format and use of units. In the United States, in spite of many (if not a majority) clinging to the Imperial units of measure, many communities (e.g. military, medicine, science, transportation, weather) routinely use ISO date-time and/or metric units of measure. Different communities have different per-measurement-type preferences (e.g. in medicine we use mm and cm quite a bit, km not so much) even within the broad scope of the metric system. This is a solved problem, with well described options. For example, while units of measurement were limited to what the OS actually used (quite reasonable), KDE4 let me configure use of ISO date-time values system wide. KDE5 apparently ignored this rather significant user requirement.
> KDE4 let me configure use of ISO date-time values system wide What you configured in KDE4 systemsettings only affected KDE4 application (those the used KLocale class). Any other Qt, GTK, or bash application used the system locale, which was not configurable. For applications based on KF5, we have abandoned KLocale, and now are using Qt to format numbers according to the locale. Unfortunately, Qt's QLocale does not allow customization yet. See also bug 340982.
some distros have solved this by now, like Manjaro or Netrunner Rolling. I guess its a bug close by now.
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This bug has been in NEEDSINFO status with no change for at least 30 days. The bug is now closed as RESOLVED > WORKSFORME due to lack of needed information. For more information about our bug triaging procedures please read the wiki located here: https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging Thank you for helping us make KDE software even better for everyone!