how to set authentication

check date
type "sudo date" enter your password

are you using live meaning from a disk or did you install it...
Well either way you already have a authentication code
You were prompted during install to supply root password and user credentials..

ok to change the time or date from GUI=desktop on gnome unless you install a different one.

go to the time/date right mouse button Adjust Date & Time
it will look faded click unlock on the next pop up enter your password click authenticate

or from prompt..
Use the following syntax to set new data and time:
date set="STRING"

For example, set new data to 2 Oct 2006 18:00:00, type the following command as root user:
sudo date -s "2 OCT 2006 18:00:00"
OR
sudo date --set="2 OCT 2006 18:00:00"

You can also simplify format using following syntax:
sudo date +%Y%m%d -s "20081128"
Linux Set Time

To set time use the following syntax:
sudo date +%T -s "10:13:13"
Where,

    * 10: Hour (hh)
    * 13: Minute (mm)
    * 30: Second (ss)

Use %p locale’s equivalent of either AM or PM, enter:
sudo date +%T%p -s "6:10:30AM"
sudo date +%T%p -s "12:10:30PM"

go to the time/date right mouse button Adjust Date & Time
it will look faded click unlock on the next pop up enter your password click authenticate

the date/time gnome upper right corner
kde bottom right..

add:
https://help.ubuntu.com/community/UbuntuTime?action=show&redirect=ChangeTimezoneHowto

https://help.ubuntu.com/community/SystemAdministration