[tz] Java & Rearguard

Guy Harris guy at alum.mit.edu
Wed Jun 5 17:39:55 UTC 2019

On Jun 5, 2019, at 3:51 AM, Stephen Colebourne <scolebourne at joda.org> wrote:

> A much smaller
> percentage of end-users care about the name of the time-zone, ie. the
> difference between Irish Time (all year round), IST or Irish Summer
> Time (summer), and GMT or Greenwich Mean Time (winter). But what those
> people care about is that the text "Irish Summer Time" is returned in
> summer. When tzdb changed its format, end-users started getting "Irish
> Summer Time" in winter, because the boolean flag had been reversed -
> thats why rearguard or a parser hack has to be used to keep the
> boolean flag as daylight=summer.

For what it's worth, a Google search of

	"Irish Summer Time" site:.ie

gets "About 921 results" and a Google search of

	"Irish Standard Time" site:.ie

gets "About 1,060 results", so I'm not sure whether, in Ireland, the correct term for time during the summer is "Irish Summer Time" or "Irish Standard Time", or whether either one are considered valid and both are used interchangeably.

If I further limit it with "site:.gov.ie", I see one reference to "Irish Summer Time":


which is a report of water levels that says

	Times are reported in UTC/GMT. Irish Summer Time is one hour ahead of this.

and three references to "Irish Standard Time":


which says

	Closing Date for Applications: Friday, 25 May at 18:00 (Irish Standard Time – UTC+1)



which says

	Please note that the closing date, for receipt of proposals from Irish HEIs, is 17.00 (Irish Standard Time) on 26 May 2017.



which says

	The closing date for submissions is 18.00 (Irish Standard Time) Monday 7 September 2015.

(and a fourth reference to the same event, but I'm not counting it separately).  (Some of those aren't the sites directly pointed to by the Google links - in one case, the page moved, and I dug it up elsewhere, and, in other cases, I de-HTTPSed the URL scheme to get Safari not to warn me that the site wasn't secure, and got redirected to another HTTPS site that didn't provoke the warning.)

So my guess is "in Ireland it's both Irish Summer Time *and* Irish Standard Time, either name's OK" is the answer.

> What almost no end-user cares about is what Irish legislation says
> (and I don't think Java should expose that knowledge).

I.e., either

	1) Java shouldn't offer a single unchanging per-zone offset from UTC


	2) if it does, it shouldn't offer any guarantee that it's the standard offset from UTC as defined by law.

I would vote for 1) here, given that a tzdb region can change what time zone it's in (which is why I don't like calling tzdb regions "time zones").

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