http://lifehacker.com/5742148/fix-windows-clock-issues-when-dual-booting-with-os-x
regedit.exe
navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation.
Right click anywhere in the right pane and hit New > DWORD (32-bit) Value. Name it RealTimeIsUniversal, then double click on it and give it a value of 1.
Lastly, reboot into OS X, then reboot back into Windows. You should now notice that your clock actually displays the correct time.
regedit.exe
navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation.
Right click anywhere in the right pane and hit New > DWORD (32-bit) Value. Name it RealTimeIsUniversal, then double click on it and give it a value of 1.
Lastly, reboot into OS X, then reboot back into Windows. You should now notice that your clock actually displays the correct time.