If you have a dual-boot setup and are switching back and forth between Windows (XP in my case) and Linux/OS X you’ll notice that Windows is unable to set the clock to the correct time after switching from Linux/OS X to Windows. This can be a real headache at times when you look at the clock and think it’s 5 hours later in the day than it actually is.

Windows sets the time to the system clock which is based on Coordinated Universal Time (UTC). I reside in Milwaukee so I’m apart of the Central Time Zone. This means that my local time here in Milwaukee is Coordinated Universal Time -5 hours (Daylight Savings Time). In order to make Windows recognize the current time without having to manually reset and synchronize the time through time.nist.gov or time.windows.com every time I booted into Windows after having played around in Linux, I had to modify the Windows Registry.

This was really easy to do. To fix the clock/time issue I had to create the following DWORD and set its value to ’1′:

RealTimeIsUniversal

within the following registry path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\

If you’ve navigated to the proper path within the Windows Registry you should see other values such as ‘ActiveTimeBias’, ‘DaylightBias’, and ‘StandardStart’. I simply right-clicked under the ‘StandardStart’ entry to get a pop up menu called ‘New’. From this menu I selected the ‘DWORD Value’ sub-menu option. I then called this new DWORD ‘RealTimeIsUniversal’. After the DWORD was created I right-clicked ‘RealTimeIsUniversal’ and selected ‘Modify’. In the ‘Value Data’ field I simply entered a value of ’1′ and clicked OK. (Remember, there’s no single quote or double quote marks, I’m using them to emphasize what needs to be done.)

The last step, you guess it, reboot. If anyone knows if Vista or Windows 7 also has the problem when using a dual-boot setup I’d be interested in learning about it especially if there’s a solution for it as well.

[June 14, 2010] EDIT: This forum post also seems to have advice on how to correct the problem by modifying the hardware clock from your terminal (Linux, etc.) — http://forum.digital-digest.com/showthread.php?postid=553203#post553203