[tz] TZ Data Base Questions

Paul Eggert eggert at cs.ucla.edu
Wed Apr 1 18:23:00 UTC 2020

On 4/1/20 8:30 AM, Dustin J. Dirth via tz wrote:

>    *   If an entity breaks off from a current time zone, does the data base fork the current time zone(A) and add a new time zone(B) with time zone B having all the historical data of A?

Yes. For the most recent example of this, see the introduction of Asia/Qostanay 
(by a split from Asia/Qyzylorda) in:


>    *   In the INANA time zone database, the file "europe" contains information for Time Zone Europe/Dublin.
> There are three lines that are proceeded with the comment "# These three lines are for when SAVE values are always nonnegative."
> These lines are also preceded by comment Delimiter (Please see below).
> Since the data follows the Comment Delimiter it is ignored on load.  Is database supposed to load this information?
> What is the purpose of these comments?

They're for converting to rearguard format, used by software that cannot handle 
negative DST. See the 'ziguard.awk' file and the Makefile rule for rearguard.zi. 
POSIX and tzcode have supported negative DST for decades, but some apps (notably 
Java-based) reportedly go belly-up with it so we have an out for them.

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