Why Does My Windows Clock Not Keep the Correct Time?by Elissa Englund
Your Windows clock is programmed to automatically synchronize to your time zone once a week. If your clock is displaying the wrong time, there are a few possible causes, including Internet connectivity problems, firewalls, or an incorrect date set on your computer.
Make sure your computer is connected to the Internet. If your computer is not online, it will not detect the correct time zone and cannot automatically synchronize to the current time.
If you are a member of a network for a corporation or other organization, your computer might be blocked from automatically synchronizing. Contact your network administrator to discuss changing your computer's time. If your computer is a home computer, your personal firewall settings might block your computer from automatically updating.
If the date on your computer has been manually set to the wrong day, your computer will be unable to automatically synchronize to the correct time. Double-click on the date and time on the bottom-right corner of your screen and make sure the date is set for today.
Internet Time Server Busy
Your Internet server might be busy and unable to synchronize at this time. If this is the case, you can force your computer to manually synchronize the date and time.
In versions of Windows older than Windows XP, the clock sometimes begins to lag if you leave your computer turned on for an extended amount of time. Try restarting your computer, which will reset the time.