When you write "I am a simple user", do you mean you do not have
administration privileges (for instance you cannot update he packages after
entering your password)?
If you do have administration privileges, then you can install the
"gnome-disk-utility" package (for instance). If the "Synaptic Package
Manager", in the "Control Center", does not work (what is worrying if you do
have administrative privileges), execute this command in a terminal ('sudo'
will ask for your password):
$ sudo apt install gnome-disk-utility
GNOME Disks allows you to format the existing partitions on your disks
(including SD cards and USB drives): click, in this order, on the disk, on
the partition and, in the menu that is a button with three gears, select
"Format partition...".
As for setting the date and time, I have no problem unlocking either GNOME
Shell's utility or MATE's (but from GNOME Shell).
