Changing start of week on LXDE calendar from Sunday to Monday

Here you can see the instructions.
https://help.ubuntu.com/community/Lubuntu/Documentation/FAQ/Guides#I_have_an_English_desktop_and_I_want_calendar_week_to_start_from_Monday_instead_of_Sunday-1

In particular, change OR add (add in my case) this

%        Added by me ===============
first_weekday   2
first_workday   2
% End of Added by me ===============

to the file

/usr/share/i18n/locales/en_US

then

# sudo locale-gen

and (as user, not root)

# lxpanelctl restart