Question on abbreviations

Paul Schauble Paul.Schauble at
Wed Sep 27 23:39:14 UTC 2006

There is also the original issue of %s being null in 1943. This seems to
be a bug. But maybe not. I'm unable from the documents I've seen to
determine the intended behavior. 


None the less, it seems obvious to me that either both the time
resulting from the transition and the letter carry forward or neither
one does. Have one but not the other carry forward seems nonsensical.





From: tz-request at [mailto:tz-request at]
On Behalf Of Mark Davis
Sent: Wednesday, September 27, 2006 4:14 PM
To: tz at
Cc: tz at
Subject: Re: Question on abbreviations


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 value?... 


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 #

Why is %s undefined in 1943? This was the question that started the 
thread. If the time setting carries forward, surely the letter should


-----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=1945.

The key to understanding is that the rules describe a list of 

After a transition, the described effect on zone offset and abbreviation
*remain* in effect until the next transition.  The "TO" part of a rule
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
> 1835 to 1916 this is undefined. If the LETTER/S are magically also 
> *before* the first FROM, that should be described in the

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 
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
> 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

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


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