Fix Your Windows Clock

by Erica Sadun

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



2006-06-19 18:12:38
This issue is so emblematic of OS X vs. Windows. The hardware clock should be set to GMT and not to local time. Why? Well GMT is "Universal". When you fly across the country with a Mac, the GMT time is still correct; only the time zone needs to be changed. When you fly across the country with Windows, the hardware clock is now incorrect as is the time zone.

But it gets more interesting at the cusps of daylight savings time. There's no such concept with GMT. So if you shut down a Mac one night, and then the local time either springs forward or falls back, and turn the Mac on the next day, the hardware clock is still correct, and it can test whether you're in or out of daylight savings time.

With Windows, the OS has to recognize that it was shut down on one side and restarted on the other and then adjust the clock accordingly. At one point Microsoft didn't get this right when the computer was left on over that fateful evening when local time "fell back". When 1:00AM rolled around it would turn the clock back an hour to midnight. And when 1:00AM rolled around again guess what happened.....

Kyle Johnson
2006-06-20 04:15:21
If you have access to a NTP (time) server, you can use that. I know Apple runs one for OSX, and I'm pretty sure MS does as well. Of course if you aren't on the internet when you reboot that won't really help you...
2006-06-20 05:48:36
Actually, this problem also applies to dual booting Linux and Windows.
But in that case, I think it makes more sense to modify how Linux treats the clock (since it has no messy registry...). Here's a link to the Debian Manual, which I imagine also applies to most Debian derivatives:
Joshua Rodman
2007-11-29 17:16:11
Unfortunately, in practice, Windows XP mysteriously will reget the "local" time from the hardware clock, and system the system time to this time. It will do this even if it disagrees with the external network sntp timesource (which is insane). I've been unable to find out what system component causes this problem.
peggy hicks
2008-03-18 04:35:06
need to fix my comp clock i'm too old yo know how