Windows stores time on the BIOS clock as Local Time, while other systems use UTC time. This means if you dual boot Windows with another system the clock will be messed up. Windows can be told to use UTC in the BIOS clock by a registry edit.
Add the key:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation]
“RealTimeIsUniversal”=dword:00000001