Time mismatching in admin section
Actually I was wrong: the database reset has nothing to do with this error.
It turns out that Django natively does not allow to change timezone for admin, because all time data used by admins is meant to have the same landmark. It's like all admins should be using the same unit of measurement.
However, as suggested here, one could set a timezone for each admin user, so that every admin sees the timedate data of the admin section expressed according to his/her timezone.