[tz] wrong Europe/Dublin dst offset rule

Ben Fortuna benfortuna at gmail.com
Wed May 30 12:16:48 UTC 2018

Hi all,

I can confirm this had also presented issues for the ical4j Java library.

I'm trying to identify a fix but looks like it the issue may be in the jdk
itself (Paul mentioned openjdk had some issues?)

If anyone has a link to track the Java issue it would be much appreciated.


On Wed., 30 May 2018, 9:54 pm Philip Paeps, <philip at trouble.is> wrote:

> On 2018-05-30 17:16:46 (+0530), Vicky wrote:
> >On Sat, 20 Jan 2018, 03:08 Paul Eggert, <eggert at cs.ucla.edu> wrote:
> >> On 01/19/2018 12:53 AM, Vicky wrote:
> >> > while parsing the data i found the issue in rule Europe/Dublin
> >> > Negative DST.. Previous version or not in any other file there is no
> >> > negative dst.
> >>
> >> Yes, although negative DST support is required by POSIX and has been in
> >> tzcode for quite some time, that was the first use of it in tzdata. That
> >> change was intended to support Irish Standard Time, which is an hour
> >> ahead of GMT (which Ireland uses in winter). We're planning to back that
> >> change out temporarily, since we found some issues with it with ICU and
> >> with OpenJDK.
> >>
> >> What software are you using to parse the data files? Has the problem
> >> been reported to the maintainers of that software?
> >
> >In current version also dst is -ve for europe/dublin
> This is correct.
> >how the dst be negative.. it is always 0 or +1. we are facing issues
> >because on this..
> Please read through the several threads on this mailing list about this
> topic since December/January.  I don't believe there is any benefit to
> having the discussion again.
> >please correct the dst for europe/dublin.
> If you can't correct your software to correctly parse tzdb files with
> negative dst, you can use the "rearguard" format of tzdb.
> As discussed (at length) though: negative dst is an unfortunate reality
> which your software should be able to deal with.
> Philip
> --
> Philip Paeps
> Senior Reality Engineer
> Ministry of Information
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