adding commands to installer image

[Bryan J Smith]

On Thu, 2009-08-06 at 10:53 +0800, John Summerfield wrote:
> I have regularly seen files timestamped  "in the future" after 
> installation, and I don't do anything extraordinary. I always run my 
> computers' clocks on local time.
> I have always assumed, "Stupid Americans, they always think the rest of 
> the world does things their way."

Actually, running the RTC on localtime is very much a legacy Microsoft
limitation / attitude.  So the allegedly "stupid American way" is
actually to run your RTC on localtime.

Open systems have traditionally run their RTC on UTC.  The idea is that
you offset everything, system, application, user, etc... localtime, from
UTC, which is the RTC.

Here's the general rule of thumb ...  
- All RTCs and most "real-time" stamps should be made in UTC
- Events should be made in the specific timezone they are local to

Remember, timezones change, and even timezone rules (offsets) change.
UTC does not.  Hence why RTCs should be UTC always, and most real-time
events stamped on UTC.

Events, on the other hand, will always be in localtime, so they should
always be stored in localtime with the reference timezone.  Again,
because timezones and timezone rules change, offsets should be made from
that stored localtime.  E.g., calendar events.

It's confusing at first, until you think through the logic.  Although
one, very required detail to the logic is that you keep your timezone
information (offset) up-to-date, so it is aware of any changes to rules.
Otherwise you run into the real issue where your localtime is either
incorrect (because the offset is incorrect), or people are changing the
localtime to the correct (which makes the UTC incorrect, because the
offset is incorrect).

UTC is absolute for RTC
Localtime is absolute for events (local to the timezone)


-- 
Bryan J Smith       Senior Consultant       Red Hat, Inc.
Professional Consulting  http://www.redhat.com/consulting
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mailto:b.j.smith at ieee.org (Blackberry / Red Hat External) 
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