Message to `tz' mailing list

Robert Elz kre at munnari.OZ.AU
Sun Feb 19 12:24:45 UTC 2006

    Date:        Fri, 17 Feb 2006 17:59:00 +0530
    From:        "N. Raghavendra" <raghu at>
    Message-ID:  <86hd6ynp83.fsf at>

  | By `tzfile', I meant precisely the binary files produced by `zic', and
  | documented in tzfile(5).  I am now able to unpack the binary files
  | correctly into Lisp objects.  Next, I should interpret the unpacked
  | data properly.

OK, that wasn't clear.   If you're working with the binary file,
then ado's reply is the one you should take notice of.   All you
need to do is find the transitions in that file that are immediately
before, and after, the time you start with - the one before then
tells you the timezone offset, name, ...   The one after is needed
just so you are sure you have found the correct "before".

The only complication is if you're trying to handle times into the
far future - when all anyone can do is guess at what the rules will
be.  If you want to accept the timezone's project's guesses (which
really just assume that the current rules will not change - which
means that they are almost certainly wrong) then you need to extrapolate
from the data at the end of the file.   That is where knowing what
the rules actually say is useful (and where you might hare about the
standard vs wall-clock vs UTC indications).   Otherwise, those things,
as ado's reply said, are simply irrelevant to you.

Jesper's reply was assuming that you (or someone) was reading the
source (tzdata) files.


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