Changing the DATE format within Whatsapp messages in Android

(note: what is written here is from my experience/opinion, using findings valid as of 2017-May-30)

Problem:
You see the date as  DD/MM/YY or MM/DD/YY and you want it the other way around.

Issue:

Whatsapp doesn't read the DATE format settings from Android's DATE FORMAT settings, but rather adjust it depending on the LANGUAGE set for Android interface.

Solution:

- If you want DD/MM/YY change the LANGUAGE of Android to English (UK)
- If you want MM/DD/YY change the LANGUAGE of Android to English (USA)

Settings > Language & Input > Language

I hope it helps.

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