Default time zone for a location (previously Europe/London)

Srdjan Krajnalic ludiskr at
Tue Sep 5 05:47:23 UTC 2006

Hi Ken,

Thank you for answering. That solution crossed my mind, but not being
thoroughly familiar with data I thought better to ask because the time zone
that appears to be appropriate is from the second rule line for the same
year, but in same cases there is only one rule to apply to the given year.
This one line still might provide the appropriate name, but again, without
knowing the data real well... Also, having a variable number of zone lines
per year makes it easier to make a mistake. 

So, if the only cases are "one or more lines, if two or more go with the
second name" that's good enough :-) You are most likely right, the present
rule line LETTERS should be the right answer in case of all
one-line-per-year rules, whether they appear as the first line, in the
middle, or as the last (or only) line.

Another thing that might be worth mentioning - the problem from the previous
letter may also occur in the middle of zone rules. For example:

Rule    Algeria 1918    only    -       Mar      9      23:00s  1:00    S
Rule    Algeria 1919    only    -       Mar      1      23:00s  1:00    S
Rule    Algeria 1920    only    -       Feb     14      23:00s  1:00    S
Rule    Algeria 1920    only    -       Oct     23      23:00s  0       -
Rule    Algeria 1921    only    -       Mar     14      23:00s  1:00    S
Rule    Algeria 1921    only    -       Jun     21      23:00s  0       -
Rule    Algeria 1939    only    -       Sep     11      23:00s  1:00    S
Rule    Algeria 1939    only    -       Nov     19       1:00   0       -

In this case, between 1921-Jun-21 and 1939-Sep-11, the need again arises to
resort to the default zone line GMTOFF. In case of Algiers, the last 1921
SAVE is appropriate through 1939-Sep-11 (0 SAVE in GMT), but in other cases
it would not be.


-----Original Message-----
From: Ken Pizzini [mailto:"tz."] 
Sent: Tuesday, September 05, 2006 12:58 AM
To: Srdjan Krajnalic
Cc: tz at
Subject: Re: Default time zone for a location (previously Europe/London)

On Mon, Sep 04, 2006 at 10:12:54PM +0200, Srdjan Krajnalic wrote:
> Here is a related question/suggestion:
> For example, when blindly processing
> Rule    Ghana   1936    1942    -       Sep      1      0:00    0:20
> Rule    Ghana   1936    1942    -       Dec     31      0:00    0
> # Zone  NAME            GMTOFF  RULES   FORMAT  [UNTIL]
> Zone    Africa/Accra    -0:00:52 -      LMT     1918
>                          0:00   Ghana   %s
> One is to apply LMT until 1918, then apply standard time zone offset 
> until the first rule. However, one does not know what time zone name 
> to apply for the given location, the best one can do is use GMT+/- based
on the offset.

This is the same as Paul's other answer: from the end of LMT until the
beginning of the Ghana rule (1936) (and again after 1942), the "standard
time" (zero savings-time offet) part of the Ghana rule is to be used, and
thus the abbreviation, according to the current rules, would be "GMT", and
the GMT/UTC offset would be 0:00 .  And again, clarification of this in the
zic manpage appears to be needed...

		--Ken Pizzini

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