[tz] Irish Standard Time vs Irish Summer Time

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Sat Dec 9 21:41:43 UTC 2017

On 2017-12-09 12:11, Paul Eggert wrote:
> On 12/09/2017 06:00 AM, Mark Davis ☕️ wrote:
>> I am worried that a significant number of implementations may keel over if
>> handed negative offsets.
> There is a tension here between trying to support daylight-saving time practice,
> and trying to keep our code and machines running. Although we want both
> objectives, they sometimes compete. Here the gain is small (supporting IST as it
> was intended). If the cost is trivial (a few formatting glitches or debug runs
> fail until software is corrected) then the gain is worth the cost; if the cost
> is large (some user programs crash in typical operation) then it's not. So far
> we've seen only trivial costs.

Does it matter what is labelled "Standard" by politicians making points?
The expectation is that if there is any deviation from standard time, it is an
advance during summer in that hemisphere, not a regression during winter.
We could just leave the zone as standard +0 daylight +1, as that data reflects
the actual situation and practice, and our concern has never been about labels.

Otherwise this is an atypical new case in the data provided by the project.
It should be flagged for downstream as a possibly breaking change for tests, and
for code on platforms not using the reference implementation.

As with removal of historical abbreviations, there is a risk of possible
downstream impacts post-release, delaying propagation of required data changes.

It would be useful if major downstream distros, vendors, and platforms could
test against the experimental repo and provide feedback prior to any release.
If testing against the experimental repo was incorporated into inter-release CI
processes, it could provide valuable pre-release feedback, and avoid "surprise"
regressions on release.

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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