Question on abbreviations

Mark Davis mark.davis at
Wed Sep 27 23:13:52 UTC 2006

My reading of the specification (zic.8.txt) was that the first rule
mentioned was operative during the interval from 1942 to "only", that is,
during 1942 alone. This was by my reading of:

     TO      Gives the final year in which the rule applies.  In
             addition to minimum and maximum (as above), the word
             only (or an abbreviation) may be used to repeat the
             value of the FROM field.

While it was explained to me what the actual code does, I don't think this
is reflected in the above text -- or at least, not at all clearly. According
to this text, if I saw the following:

Rule    US    1942    1944    -    Feb    9    2:00      1:00    W # War

The rule should not apply in 1945. So I request that the text be fixed,
because the rule clearly, according to the explanations given on this
thread, applies *afterwards* (and the circumstances in which it applies need
to be clearly specified. Is it until the next Rule that has an SAVE value
with the same SAVE value as this Rule? Until the next Rule that has a SAVE


On 9/27/06, Paul Schauble <Paul.Schauble at> wrote:
> So in this case:
> Rule    US    1942    only    -    Feb    9    2:00      1:00    W # War
> Rule    US    1945    only    -    Aug    14   23:00u    1:00    P #
> Peace
> Why is %s undefined in 1943? This was the question that started the
> thread. If the time setting carries forward, surely the letter should
> also.
>     ++PLS
> -----Original Message-----
> From: tz-request at [mailto:tz-request at]
> On Behalf Of Ken Pizzini
> Sent: Wednesday, September 27, 2006 3:14 PM
> To: tz at
> Subject: Re: Question on abbreviations
> On Wed, Sep 27, 2006 at 02:37:58PM -0700, Mark Davis wrote:
> > I share your confusion. If Paul (Eggert's) description is right, then
> I have
> > to ignore the TO field in some circumstances which are entirely
> unclear to
> > me. I would much rather see the TO field corrected. That is, if
> TO=1942 is
> > ignored, and 1945 is the real date, then the line should be corrected
> to
> > TO=1945.
> The key to understanding is that the rules describe a list of
> *transitions*.
> After a transition, the described effect on zone offset and abbreviation
> *remain* in effect until the next transition.  The "TO" part of a rule
> is
> used to enable a shorthand for a _recurring_ transition, such as "first
> Tuesday of February", for all years within the range.  If "to" is
> "only", then the *transition* being documented is a singleton, but
> the transitioned-into offset/abbreviation remains in effect until the
> _next_ transition, no matter how far in the future.
> > There are other failures in the parsing. My error messages are:
> ...
> > I looked into why this is happening, and found:
> >
> > Zone Europe/Amsterdam    0:19:32 -    LMT    1835
> >            0:19:32    Neth    %s    1937 Jul  1
> > But the first LETTER/S defined by Neth is in 1916, so during the range
> from
> > 1835 to 1916 this is undefined. If the LETTER/S are magically also
> defined
> > *before* the first FROM, that should be described in the
> specification.
> Yes, this is a failure of the documentation.  If a Zone refers to a time
> within a Rule that is before the first transition mentioned for that
> rule,
> then the _oldest_standard_time_ "Letter/s" is used.  In this case, AMT.
> > BTW, the documentation was a first a bit confusing to me, since it
> says that
> > fields are delimited by spaces, and lists a single Zone UNTIL field.
> > However, if you look carefully at the documentation, there are really
> 4
> > fields:
> >
> >
> > which are optional [but only in "truncation" from the end: that is, it
> > corresponds to the (Perl) regex (UNTIL_YEAR (UNTIL_IN (UNTIL_ON
> > (UNTIL_AT)?)?)?)?].
> >
> > I'm not the only one to have initially made this mistake: the proposed
> > format for the TZ database makes the same mistake.
> Confusing: granted.  Whether "Until" is one or multiple fields is a
> matter of interpretation.  The _traditional_ understanding is that it
> is a *single* "timestamp field" which may happen to have spaces within
> it.  BTW the subfields aren't "YEAR IN ON AT", but "YEAR MONTH DAY
> TIME".
> In this regard, a recent addition to the tzcode tarball is
> which translates the more free-with-spaces zone tzdata into a form which
> strictly uses a single tab between fields.  This may make life easier
> for some by simplifying their parser's requirements.  (Or not.)
>                 --Ken Pizzini
-------------- next part --------------
An HTML attachment was scrubbed...

More information about the tz mailing list