[ntp:questions] Automatic time synchronization of local hw clock.

Jochen Bern Jochen.Bern at LINworks.de
Sun Apr 20 17:45:38 UTC 2014

On 20.04.2014 14:00, questions-request at lists.ntp.org digested:
> From: David Taylor <david-taylor at blueyonder.co.uk.invalid>
> It would be helpful if the operating systems were to agree on how to use 
> the BIOS clock.

Well, if I understand the statements about Win correctly, they *do* now,
at least in their current versions.

> Not every computer travels during the year

Traveling computer with a localtime RTC: Problem.

Multi-boot computer with RTC using a localtime with DST: Problem.

Computer produced abroad having its RTC set to localtime there: May
prove a problem. (Very real support cases over here. We're now seriously
pondering to have the firmware-generated CAs *lie* and make certs'
validity start a day or more *before* what the appliances consider "now"
at the moment the request button's pressed.)

Computer with UTC RTC: ... um. Problem? See below ...

> and not every location has summer-time transitions.

Actually the *majority* of places on this planet do *not* use DST *now*:
(Unless you want to split hairs and call Russia "using DST, only all
year 'round", I suppose.)

Doesn't matter, either. Errors are minimized by taking an approach that
is 100% *technically* consistent and feasible, and basing computer
systems' "core" time on a global, continuous, non-overlapping notion of
time (*) *independently* of whether the local legislator sees the same
light is just that.

(*) The issue of leap seconds notwithstanding.

> Most users would likely be very confused were they to see the BIOS clock 
> time in UTC!

Any user feeling a need to "correct" the RTC to his local time would
also immediately agree (but hopefully not *remember*) that he should
check back when DST switching occurs, and effect that himself if it
doesn't occur automagically (which it won't while he's in the BIOS
monitor). Please elaborate on how you want an RTC-is-localtime OS to
successfully counteract *that* act of sabotage. Teaching users that
things like a "world time" exist may prove easier IMHO. (Might be a
suggestion to have such a hint added to the BIOS tools, though.)

								J. Bern
*NEU* - NEC IT-Infrastruktur-Produkte im <http://www.linworks-shop.de/>:
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Jochen Bern, Systemingenieur --- LINworks GmbH <http://www.LINworks.de/>
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