[Xastir] Daylight saving time?

[Curt, WE7U]

On Wed, 21 Mar 2007, Mike Fenske wrote:

> Might be a problem with my old SuSE 7.3 system, but I noticed
> today that in the "Station Info" window, the "Last Heard" time
> seems to be out by one hour, i.e. showing 07:45 instead of 08:45.
> I did update my time zone settings to the new daylight saving
> scheme and my system shows the correct time. System clock is GMT.
> Is this an Xastir problem or my time zone settings??

Hard to say.  I've learned a lot more about timezone files and
settings in the last few weeks than I ever cared to learn, but not
because of Xastir problems.

Here's what I've gleaned so far:

BSD-derived systems use either "Olson" or "POSIX" timezone
files/code.  I can't remember which, but it's just ONE of those two
listed.  I think it was "Olson".

System-V derived systems may use both sets.  Here are the two
formats and commands to try them out:

    TZ=PST8PDT date
    TZ=US/Pacific date

Do you get two different answers?  I don't on Linux, but do on
Solaris, on systems which have had new timezone files applied
("Olson") and been rebooted.

PST8PDT is a POSIX time and it comes from the libc on the system in
Solaris' case.  It takes both an update to libc and new timezone
files to fix both sets of timezone code.  Fun huh?  For those
running old unsupported versions of Solaris, the only remedy is to
update the timezone files and then make sure NOT to use the PST8PDT
format for TZ.

Let's see, what else have I learned?  Oh yea, the port 13 and port
37 time servers on Solaris must also depend on libc as they were
wrong and I had to turn them off.

Setting TZ=US/Pacific when starting any app usually fixes the
problem.

Crond can get confused if you go backwards in time, needing a
restart.  Going forwards in time crond might miss running some stuff
if they're scheduled at the wrong time of the morning the day of the
timechange (that last is very normal and not a bug).

Basically if you're running supported OS'es, you may need updates to
your OS to fix timezone-related problems.  If you're running
unsupported, you may have problems crop up which can't be fixed
easily.

As far as Xastir, it queries the OS for the time constantly.  Xastir
has problems if you go backwards by an hour, but shouldn't have any
major problems if you jump forwards by an hour.  It might get real
busy for a few seconds at the time of the jump, but then things
should settle down.

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
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