Where should DATETIME_FORMAT be placed for it to have effect on the display of date-time in the Django admin site (Django’s automatic admin interface)?
Documentation for
This will solve the particular problem that is not possible with DATETIME_FORMAT (as it is ignored in the current Django implementations despite the documentation), is dirty too and is similar to ayaz's answer (less global - will only affect the admin site list view):
Right after the line
(date_format, datetime_format,time_format) = get_date_formats()
in file (Django is usually in folder Lib/site-packages in the Python installation)
django/contrib/admin/templatetags/admin_list.py
overwrite the value of datetime_format (for a models.DateTimeField in the model):
datetime_format = 'Y-m-d H:i:sO'
And for date-only fields:
date_format = 'Y-m-d'
Restart of the web-server (e.g. development server) or logging out of the admin interface is NOT necessary for this change to take effect. A simple refresh in the web-browser is all what is required.