On Wed, 22 Sep 2004, Rodolfo J. Paiz wrote: > On Tue, 2004-09-21 at 16:30, Jeff Vian wrote: > > Windows resets system time with the daylight savings time changes (twice > > a year). Linux leaves system time alone and makes the change in > > software to display DST. When you do dual boot in an environment where > > DST is used you will see this discrepancy. > > > > I know of no way to make the two systems play nice together as relates > > to time. > > > > Simple: Since Windows will set the hardware clock to local time, simply > tell Linux that the hardware clock does *not* use UTC. Configure the > time zone and DST correctly in both OS's. > > Now that Linux and Windows both expect the hardware clock to represent > local time, both will attempt to keep it correct at that setting. No > further problems should occur. > > Cheers! Unfortunately, no. If you are running Linux with the hardware clock set to LOCAL at the time change, then Linux will make the change successfully. If you then reboot to Windows, Linux updates the hardware clock on shutdown. When you next boot into Windows, it will realize that it's the first boot since the change and adjust software and hardware clocks again. Now you are an hour off in Windows, and when you boot Linux, it assumes the hardware clock has the correct local time, so you're an hour off there too. If you are booted into Windows at the time change, Windows happily adjusts the hardware clock and all is well. If the machine is off at the change, Windows will adjust correctly if it is booted first, and Linux will assume that the hardware clock contains the correct local time and will be OK. If you boot Linux first and don't adjust the hardware clock from the BIOS, you're off by an hour. If you do adjust the clock in the BIOS and then boot to Windows, then Windows will detect that it's the first boot since the change and adjust the clock again. Voila, an hour off. Even if Linux tried to be clever and adjust the clock on first boot after the change, Windows would do the same, and damnit, you're off by an hour again. This would all be simpler if Windows knew what to do with a UTC hardware clock. The closest I've been able to come is to tell Windows that the local time *is* UTC (i.e., GMT with no DST). The only thing wrong with that is that Windows doesn't show the true local time, but I don't really care about that. The other consistent way to handle things is to make sure that you aren't running Linux at the change and that you boot Windows first after the change. All else requires thinking ahead and adjusting the clock in the BIOS. -- Matthew Saltzman Clemson University Math Sciences mjs AT clemson DOT edu http://www.math.clemson.edu/~mjs
