What heavyd posted is correct. Your PCs are likely referencing your domain controller for their time settings. I would recommend checking and resolving any issues your domain controller has with its own time settings, but if you want to make changes to this specific computer you can either:
1) Edit your registry to pull time from an outside source. (such as time.windows.com) The change you have to make in regedit is: HLMC\SYSTEM\Currentcontrolset\Services\W32time\Parameters - look for the REG_SZ entry named "Type" and change the value from NT5DS to NTP.
2) You can also change that same registry key to NoSync instead, and this will stop your computer from referencing any outside source and simply run with the time you specify.
A reboot will be required after making either change.