Re: [SLE] Daylight Saving time change?

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The Monday 2006-10-30 at 08:03 -0600, Stevens wrote:

If Carlos would note in my original reply that I said
"... it's all relative", then some sense can be made of this
mess about time, clocks, etc.

First of all, any _nix system only knows the time if you
tell it what it is (actually, that's true for any puter). The cmos
clock on the mb is generally referred to as the hardware
clock and can be read with "hwclock -r". In my system
the hc value is tested against the settings in /etc/adjtime
and the result is presented to the system for use: display,
cron, etc. Here's the relative part: the system thinks it is
default UTC, but you can have it believe anything. The
correct UTC might be 3am but you can have it set to 9pm.
All the system will do is apply local time zone offsets from its
perceived utc value IF "local" is included in adjtime.


The fact that the "adjtime" file contains the word "local" doesn't affect
in any way the the internal, system, or software clock (all names for the
same clock), which still maintains UTC, regardless of that file.

The "local" or "utc" word in that file means that the CMOS, or Hardware,
or Bios clock (all names for the same device) stores local or utc time. It
is used only during boot (man hwclock).


You are confusing concepts.

It is true you can lie to the system and tell it a different hour. Right.
But it is a very difficult lie to maintain. For instance, the moment you
fire up any network time setting program, it will adjust your clock to
UTC, internally - unless you modify the sources of such a program.

The internal time is simply a counter storing the number of seconds
since 00:00:00 UTC, January 1, 1970 (man time).

Based on that internal time, when the time is displayed to the user,
the local time is calculated from the time zone and dsl settings (ie,
your locale). You can have many different time zones in use, one for
each user of the system.

If you set the internal time to something else than UTC, when the time is
displayed the system will add to it the displacement known from UTC to
Local time - therefore, you will have to give your setup a different time
zone than the real one so that the time displayed appears to be correct.

No, the internal clock will run UTC. Even if I set it up giving it my
local time, it does a calculation and internally sets UTC time. You can
not change it unless you modify the kernel sources and many other
programs. Did you?


So, don't say that a _nix internal clock is UTC when, in fact, it
is whatever you want.

Utterly impossible.

UTC is French for Universal Coordinated
Time,

No, it is English for "Coordinated Universal Time". The initials were
chosen so that the order is incorrect both in English as in French, on
purpose, so that no one could claim that UTC was "theirs".

- --
Cheers,
Carlos E. R.

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