[tz] Java & Rearguard

[Guy Harris]

On Jun 2, 2019, at 11:39 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:

>> Paul, how should we go about requesting an interpretation from TOG here?
> 
> I could do that, but I don't see what sort of interpretation is needed.

An interpretation to indicate whether "tm_isdst" means "is Daylight Saving{s} Time", for "Daylight Saving{s} Time" presumably meaning "the clocks are turned forwards for late spring and summer", or means "is the alternative timezone", in the sense of "alternative timezone" from the "Environment Variables" page section on the TZ environment variable, is needed.

> POSIX clearly requires support for a TZ setting like 'IST-1GMT0,M10.5.0,M3.5.0/1' that specifies negative DST, and that is true regardless of what Ireland happens to be doing right now.

But, with that TZ setting, does it:

	1) require that tm_isdst be 1 from 1AM Sunday in the last week of October until 1AM Sunday in the last week of March, because that's the "alternative timezone";

	2) require that tm_isdst be 1 from 1AM Sunday in the last week of March until 1AM Sunday in the last week of October, because that's when the clocks are turned forward - or, rather, *aren't* turned *backward* from standard time;

	3) say it's implementation-specified which of those is the case?