Is it possible to easily create a custom system format? If not, such a feature would be a great addition

[SuppaMan (Paul Kim)]

This is the system Format tab in system settings under Language & Region

I am a Korean American who prefers English and the Metric system.
I want to have a specific system format. An example like so.

Dates. 1990 Jan 17 Mon

Times HH MM SS

Dates & Times YYYY MM DD Name Of Date HH:MM:SS

Numbers 1234,5678.900

Measurement Metric

Paper A4

Currently, you can only use country-specific formats and cannot make ones yourself. This is very annoying as someone who grew up in different countries and travels.

If this feature is not currently available, adding it to a future release might be useful.

P.S.
Korea typically uses a comma between 4 numbers like nnnn,nnnn.nn not nnn,nnn,nnn.nn
Source: and Korean American and lived in South Korea for 20 years.

[jtojnar (Jan Tojnar)]

g-c-c uses localed to control locales. There does not seem to be an option for more fine-grained settings in the GUI but you should still be able to override individual categories through CLI using localectl.

For example, I chose Czech locale in Settings but overridden the system language with localectl set-locale LANG=en_GB.UTF-8.

See GNU gettext utilities: Locale Environment Variables for the variables and also LANGUAGE variable, which is useful when you want to configure fallback language.

[SuppaMan (Paul Kim)]

I see. As it stands out, there is no method to change it directly in settings similar to KDE?