You can define the
LC_TIME environment variable. In
~/.profile if you start you session in a login shell or else
% LC_TIME=ru_RU.UTF-8 date
Сб 07 окт 2023 13:39:21 CEST
will make the output format be in Russian,
That only works if you already have that locale enabled (or, better said, generated), which you can check with
locale -a. If it is not generated yet, find the corresponding line in
/etc/locale.gen, remove the
# from it and run
In a desktop environment, there might be a corresponding option in the localization settings.
All the environment variables heeded by
date specifically are found in the POSIX specification.
And the locale section lists the variable in more details, as well as which other functions must respect it.
There is an expectation, but not a guarantee, that time related programs and functions will respect that variable.