[tz] Irish Standard Time vs Irish Summer Time

Paul Eggert eggert at cs.ucla.edu
Sat Jan 20 00:53:49 UTC 2018

On 01/19/2018 03:13 AM, Neil Fuller via tz wrote:
> If the Europe/Dublin change "sticks" in tzdata, the likely course for 
> supporting existing devices would be to patch the Android tzdata and 
> pretend the Europe/Dublin shift hasn't happened. Future devices could 
> potentially support negative DST adjustments if all the problems are 
> caught in advance.

Yes, this would be one route forward, after 2018c comes out. (2018c will 
roll back the Irish changes temporarily.) That is, the idea would be to 
have a good way to generate a variant of the zi files that does not use 
negative DST offsets.

Android currently doesn't support time stamps after 2038, right? So 
another approach would be a hack to add a table that works for current 
Android while still matching the desired behavior, by listing explicit 
transitions for each year through 2037. Something like the attached, 
say. (I have not tested or installed this patch and it won't be in 
2018c; I'm floating it here just as an idea.) The advantage of this 
latter approach is that Android would agree with post-2018c tzdb 
behavior (including tm_isdst flags) for all time stamps that Android 
currently supports.

PS. Thanks for the details about some of the problems on the Android 
side; I now understand a bit better what you're up against.

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