I user může změnit systémový čas v biosu, ale to jsi asi nechtěl slyšet.

Takže:

First, you need to have the “Change the system time” privilege. Run “Local Security Settings” (as admin), navigate in the left pane to Security Settings \ Local Policies \ User Rights Assignment. Double-click on “Change the system time” and add users or groups. You can also specify “INTERACTIVE”, which will allow whoever is logged on to the computer to change the date and time. You need to log off and back on for the change to take effect.