I wish to set LANG only by default
When I log into GNOME desktop, it sets LC_TIME, LC_NUMERIC, LC_MONETARY, LC_MEASUREMENT, LC_PAPER however I'd unset those variables and set LANG only since I run applications with LANG.
E.g. env LANG=fr_FR.UTF-8 gedit
or :r!env LANG=C date
in vi mode or else.