[tz] [english 100%] Re: [english 100%] Re: OpenJDK/CLDR/ICU/Joda issues with Irelandchange

[Stephen Colebourne]

On 26 January 2018 at 07:46, Paul Eggert <eggert at cs.ucla.edu> wrote:
> Meno Hochschild wrote:
>>
>> I have adjusted my tzdb-compiler (Time4J) such that it looks if all rule
>> lines referencing the same name (here: Eire) contain any negative dst
>> offsets. If yes then let's assume summer time for SAVE=0 and winter time for
>> SAVE < 0. So I can still work with old unchanged CLDR-entries for getting
>> "Irish Standard Time" in summer.
>
>
> This sounds like a good idea regardless of whether we make changes to zic
> input. Couldn't OpenJDK do the same?

Such an approach is merely adding an even more subtle API to TZDB, one
where a mixture of positive and negative SAVE values would cause
chaos.


> I'm somewhat leery of changing zic
> input format to address this problem, particularly if a simpler workaround
> is available.

Meno's approach with an extra column actually tackles the heart of the
problem by providing a stable key that can be used to link the two
projects. This decouples TZDB from CLDR. TZDB can make its change,
while CLDR can still refer to CMT as standard and IST as daylight (as
required by CLDR compatibility).

A downstream parser would have to note the negative SAVE and META
information, and re-calculate the raw offset. A pain, but do-able. And
META is the only way to handle ramadan-like changes.

Stephen