How to coordinate the clock when dual-booting with Windows

Peter Silva peter at
Sun Dec 10 15:57:51 UTC 2017

can confirm, at least in older versions of windows, localtime
(whatever timezone was set) was the time saved in the bios.  Dunno if
current windows versions have smartened up, but it never used to store
in UTC.

I agree that the sensible thing to do is for all OS's to always store
time in UTC at the hardware level and do the timezone in the OS, but
that's not how it was done before, might have improved in recent

On Sun, Dec 10, 2017 at 10:52 AM, Colin Law <clanlaw at> wrote:
> On 10 December 2017 at 15:45, Liam Proven <lproven at> wrote:
>> On 10 December 2017 at 10:42, Colin Law <clanlaw at> wrote:
>> >
>> > The clock is not normally an issue when dual booting.
>> It bally well is for me!
>> E.g. if it's set to local time, both OSes move the system clock
>> forward or backwards when daylight savings times begins or ends,
>> resulting in a 2h discrepancy.
>> My solution: minimize use of Windows. I boot it a couple of times a
>> year, if that, normally.
> Interesting, I have never seen that. I assumed the system clock was in UTC,
> and so would not change with DST.  You may be right about that though, I
> have no evidence either way. However I would have thought it would re-sync
> the next time ntpdate or whatever it is that does the auto timesync ran.
> Colin
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