Time zone confusion and implementation hints

[Robert Elz]

    Date:        Wed, 07 Jul 2010 07:47:38 +0200
    From:        Yves Goergen <nospam.list at unclassified.de>
    Message-ID:  <4C3414FA.4010005 at unclassified.de>

  | Hm, so I need to figure out how to parse that rule and compute further
  | data myself.

The rule is POSIX specified, so you can look up its definition - but you'll
also find the code to process it in localtime.c somewhere.   You could just
use that - it isn't very difficult, just tedious (much much easier than
parsing the tzdata source files!)

  | I'm using zic to not do that. I hoped there would be a
  | simple switch in zic.c where I could extend the last generated year.

There isn't, but you could fairly easily add one, you just need to alter
its setting of max_year (look for "2037" in the code).   The advantage of
using the rule is that you can generate transitions for any future year
that seems useful (with no guarantee of correctness - but few people expect
us to cope with unannounced legislative changes before they happen).  That
is, you don't have to have an upper bound (for a calendar application, a
backwards limit is generally OK, as no-one wants to plan meetings in the
past - but planning future events many years ahead is sometime desireable).

kre