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Date:      Mon, 10 Apr 1995 12:56:02 -0400
From:      Garrett Wollman <wollman@halloran-eldar.lcs.mit.edu>
To:        uhclem%nemesis@fw.ast.com
Cc:        freebsd-bugs@freefall.cdrom.com
Subject:   bin/327: Clock management punishes you if CMOS != GMT		FDIV020
Message-ID:  <9504101656.AA03250@halloran-eldar.lcs.mit.edu>
In-Reply-To: <199504092021.NAA01474@freefall.cdrom.com>
References:  <m0ry2ND-0004upC@nemesis.lonestar.org> <199504092021.NAA01474@freefall.cdrom.com>

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<<On Sun, 9 Apr 1995 13:21:01 -0700, uhclem%nemesis@fw.ast.com said:

>> Number:         327

> If you elect to keep the CMOS at local time, the installation will offer
> you cities (not many choices in CST by the way), then show you a time with
> the CST suffix, WITH THE GMT OFFSET ADDED even if you don't want it.

The first thing it asks you is:

	Is $4, $1 $2 $3 $6 the correct current date and time?

(with appropriate values for the positional variables).  If your CMOS
clock is set to local time, then this will be the current time, and so
you are supposed to answer `y'.  It then tells you:

	Unless your local time is GMT, this probably means that your CMOS
	clock is on local time.  In this case, the local times that you will
	be shown will be incorrect.  You should either set your CMOS clock to
	GMT, or select option 98 from the main menu after selecting a
	timezone.

Can't get much more explicit than that.  Note that we VERY EXPLICITLY
do not allow users to select something like `CST' as their timezone,
because the notion is not well-defined.  Instead, we ask:

	Please select a location from the following list which
	has the same legal time as your location:

This is a very different question, because the time zone database
keeps track of summer time arrangements and changes in zone
boundaries.  Thus, for most of the U.S. locations that observe
``Central time'', `Chicago' is the correct choice, because most
locations in that area started observing both standard and summer time
at the same time as Chicago did.  Most parts of Indiana started out
with Eastern, summer time, but in 1946, Indiana decided not to observe
summer time, and so those locations use `Fort_Wayne'.  Starke County,
Indiana, used to be on Central time following the `Chicago'
definition, but in October 1991 it decided to follow the rest of
Indiana and be on Eastern time all the time, with no summer time;
hence, `Knox_IN'.  Michigan has always been in the Eastern zone, but
didn't observe summer time from 1968 to 1973, hence `Detroit'.

At some point in time, I'll re-do all this a la `dmenu'.  (Or Jordan
is welcome to...)  It's all explained in gory detail in
/usr/src/share/zoneinfo.

> It then asks "Is this what you wanted?".  The normal user isn't going to
> realize that all the installation process is asking about at that point is
> the CST suffix and will answer the question NO because the time is wrong.

I agree that there is a problem here, but there's nothing we can do
about it, since we can't correct the time without knowing what the
user's timezone is.  I probably should have asked ``Is this the time
zone you wanted?''

> Also note that if you have CMOS set to LOCAL, and boot the system in maint
> mode, the date shown is wrong (behind by several hours).

Another good reason to use a UTC CMOS clock...  There's no other way
it can work the way you want it.

-GAWollman

--
Garrett A. Wollman   | Shashish is simple, it's discreet, it's brief. ... 
wollman@lcs.mit.edu  | Shashish is the bonding of hearts in spite of distance.
Opinions not those of| It is a bond more powerful than absence.  We like people
MIT, LCS, ANA, or NSA| who like Shashish.  - Claude McKenzie + Florent Vollant



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