date and time error ?

i get this message when trying to use my licenser … The date/time settings of this computer seem to be incorrect.

Please verify your computer’s date, time, and time zone settings and try again later, or contact your software vendor’s support department in case the problem persists.

Click ‘OK’ to proceed with further maintenance tasks, or click ‘Cancel’ to stop the maintenance procedure.

How do I verify my date and time ???