You can add more languages to your system easily and change regional formats independently to language.

Set language

Debian/Ubuntu

  1. Run sudo dpkg-reconfigure locales and follow the steps. You may need to reboot or log out.

Arch Linux

  1. Add languages by editing /etc/locale.gen. Uncomment the languages you want to install. 
    ...
#en_SG ISO-8859-1
en_US.UTF-8 UTF-8
#en_US ISO-8859-1
...
  2. Run locale-gen to load those languages. 
    $ sudo locale-gen
Generating locales...
  en_US.UTF-8... done
  es_ES.UTF-8... done
Generation complete.
  3. Set your system language by editing /etc/locale.conf. Add LANG= and the language code. 
    LANG="en_US.UTF-8"
  4. Reboot.

Set keyboard layout

Debian/Ubuntu

  1. To set your keyboard layout, run sudo dpkg-reconfigure keyboard-configuration. You may need to reboot or log out.

Arch Linux

  1. To set your keyboard layout, edit /etc/vconsole.conf and add KEYMAP=<keymap>. Run localectl set-x11-keymap <keymap> to set keyboard layout for X11.

  2. Changes will take effect in next boot.

Other regional parameters

Arch Linux

You may need to change some regional parameter like date format or measurement units. You can do it by adding more lines to /etc/locale.conf with the region you want to use for every parameter, for example:

LANG="en_US.UTF-8"
# This will allow to use millimeters instead of inches
LC_MEASUREMENT="es_ES.UTF-8"
# This will allow to use A4 instead of US letter
LC_PAPER="es_ES.UTF-8"
# This will make Monday the first day of the week (may change week day language)
LC_TIME="es_ES.UTF-8"

If you want to change language settings on a user-level, you can edit your ~/.bash_profile and add the environment variables.

LANG="en_US.UTF-8"
export LANG

If you have any suggestion, feel free to contact me via social media or email.