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Date: Sun, 28 Oct 2007 18:08:26 +0700
From: Eugene Grosbein <eugen@kuzbass.ru>
To: Peter Jeremy <peterjeremy@optushome.com.au>
Message-ID: <20071028110826.GA83337@svzserv.kemerovo.su>
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Cc: stable@freebsd.org
Subject: Re: CMOS, daylight saving time and dual-boot
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On Sun, Oct 28, 2007 at 09:35:08PM +1100, Peter Jeremy wrote:

> Based on a quick check, it doesn't look like adjkerntz(8) can handle
> your situation.  In the absence of any independent time source, it's
> actually very difficult to handle this situation.  In theory, it would
> be possible to note that the last system shutdown (or last time the
> RTC was set) and determine whether there's been a DST transition in
> the period between then and now and adjust the RTC appropriately (I
> believe Windows does this).  The problem is that, unless this record
> is kept within the RTC and all OSs co-operate in its meaning, each
> OS will independently adjust the RTC when it is next rebooted (and
> I believe multi-boot PCs run into this problem).

It would be possible to utilize a bit in the CMOS at boot time
to decide if BIOS time set to Summer time and clear it appropriately,
in theory :-)

Eugene