MacOS/WinXP dual system clock errors

When you have both Mac OSX and Windows XP/Vista on your computer, you will notice that the clock will change when you switch between two systems. This is due to that Mac treats the hardware clock(shown in BIOS) as GMT time while windows treats that as local time. The solution is then to make them agree with each other.

To make Windows take GMT time
Create a file, for instance, clockfix.reg, as

Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation] "RealTimeIsUniversal"=dword:00000001

and run it (by double-clicking).

To make Mac OSX use local time
First you'll need to add a line to /etc/rc.local:

date `date -u +%m%d%H%M%Y`

And to /etc/rc.shutdown.local you'll need to add this:

date -u `date +%m%d%H%M%Y`

Update: for leopard (10.5.x), the above method doesn't work. Please follow the instruction in this link.