Change default locale in Debian Linux

Change locale in Command line

Commands:
dpkg-reconfigure locales
locale-gen en_US.UTF-8


GNOME

Go to GNOME - System > Administration > Language Support


KDE

Go to KDE - System Settings > Regional & Accessibility > Country/Region & Language


Files
Default locale: /etc/default/locale
Generated locales: /etc/locale.gen
Available locales: /usr/share/i18n/SUPPORTED
/var/lib/locales/supported.d/local