Is your Windows clock getting confused by rebooting? Over at the Apple Discussions board, they’ve found a solution for messed-up Macteltosh clocks during the Windows boot process.
The problem with the Windows clock being off is because the hardware clock (the one on your actual motherboard) is being set to “Universal” time, or GMT, when you shut down your MacOS bootup. When you boot Windows, Windows assumes your clock is set to your local timezone because that’s what Windows does by default. This explains why the people who set their MacOS clock to GMT got the right time in Windows… If the hardware clock is being set to “GMT,” when it’s actually the local time, Windows will pick this setting up as local time as it did before.
To fix the problem you’ll need to edit your registry, so proceed very carefully. Full instructions here