[tz] OpenJDK/CLDR/ICU/Joda issues with Ireland change
Michael H Deckers
michael.h.deckers at googlemail.com
Sun Jan 28 19:00:06 UTC 2018
On 2018-01-26 22:16, Paul Eggert wrote about the tzdb dst bit:
> On 01/26/2018 01:39 PM, Michael H Deckers via tz wrote:
>> Before this change proceeds, it is, in my opinion, necessary
>> to obtain agreement on what the new significant (non-vestigial)
>> role of the dst bit, if any, should be in the future (beyond the
>> single case of Ireland).
>
> I don't think there's much disagreement over what the bit means in the
> context of the POSIX API. For example, POSIX specifies that this
> environment setting:
>
> TZ='IST-1GMT0,M10.5.0,M3.5.0/1'
>
> means that standard time is abbreviated "IST" and is 1 hour ahead of
> UTC, that daylight saving time is abbreviated "GMT" and is at UTC, and
> that the European Union's current rules are in place for when to
> change UTC offsets. tzcode and every other POSIX-compatible system
> support this, and set tm_isdst=1 in winter with a negative DST offset
> when operating in this locale. As far as I know there's no serious
> dispute about this, nor is anybody seriously proposing to change this
> behavior. That is, the tm_isdst API may be vestigial, but it's too
> late to change what it means.
>
No, no: POSIX does not say anything about the setting of the
tm_isdst member for a given TZ string;
nor does it talk which part of the TZ string describes daylight
saving time. I am reluctant to accept
any assertion of the type it is clear that POSIX means XXX without a
specific reference implying it;
if I have to write reliable code, I have to know exactly what I can
rely on.
Michael Deckers.
More information about the tz
mailing list