Changing time on a Windows machine isn’t tough at all unless the machine is hooked to a Domain. In this case you may need to set the time on the server and then have the individual computer resync their time.
Here is the command line for setting the time to pull from a external source.
w32tm /config /manualpeerlist:time-a.nist.gov /syncfromflags:manual /reliable:yes /update
Then restart the Time services
net stop w32time
net start w32time
Lastly resync the time.w32tm /resync
Let us know if this helped you....