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I've got a rig with 2 hard drives. I've put Ubuntu 9.04 (Jaunty) on one of the drives and Windows Vista SP2 runs on the other drive. I went with this approach rather than dual boot since I wanted to be able to swap out the OSes as I please and just keep things clean and separate.

The problem I've been noticing is that when I am in Ubuntu and I reboot into Windows Vista (by selecting the Vista drive at boot time), the Vista clock is always set back by about 5 hours. Also I've noticed that when I try to synchronize the Vista clock, it always errors out on the first attempt, then I have to click "Update now" a second time before the synchronization with the selected NTP server takes effect. Repeated reboots of Vista do not affect the Vista clock so long as I go from Vista back to Vista each time.

Also, the reverse is not true, that is, rebooting Vista and launching Ubuntu does not affect the Ubuntu clock.

I can't figure out why this is happening. Would appreciate any help at all.

Update: I should also probably mention that Ubunty is 64-bit and Vista is 32-bit.

Dave Cheney
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kpax
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  • This is an old Linux/BSD and Windows dual boot issue. I would suggest editing the question to reflect the generic nature of the problem. – pcapademic May 31 '09 at 08:54
  • Like I mentioned, the 2 OSes are *not* in dual boot, they're on separate SATA hard drives. – kpax May 31 '09 at 13:37
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    They *are* in dual boot because you boot either one or the other. Dual boot does not mean "in the same hard drive", even if that setup is the most common. – njsf May 31 '09 at 14:18
  • I always thought multiple drives each with their own OS was called a multi-boot configuration. Anyway I must be mistaken. Thanks for the clarification. – kpax May 31 '09 at 15:38

2 Answers2

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Is it this problem?

You need to look at
/etc/default/rcS
and change UTC=yes to UTC=no.

This makes Ubuntu read and write to the hardware clock in the same way as Windows, using local time instead of UTC.

Adam
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If you prefer to make the change to the windows installation:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation]

Add a new dword named "RealTimeIsUniversal" and set it to 1

Tim Matthews
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  • I'd already tried the "accepted" fix which worked for me. – kpax May 31 '09 at 13:38
  • This would have the added benefit of working if you forgot to change the timezone information after a move. – Brad Gilbert May 31 '09 at 15:58
  • I've done this, but every now and then my Windows clock jumps back 6 hours (I'm UDT-6). I then have to go in and have it re-update with the time server. – Tom Mayfield Aug 22 '11 at 19:12