[tz] Extra transition for Europe/London with 2023d

[Guy Harris]

On Jan 6, 2024, at 3:35 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:

> On 2024-01-06 14:51, Guy Harris via tz wrote:
> 
>> POSIX's time API has no notion of "gmtoff" and "stdoff".
> 
> Although that's true for current POSIX, POSIX 202x/D3 does have tm_gmtoff in struct tm, as a result of Austin Group Defect 1533 <https://austingroupbugs.net/view.php?id=1533> which saw steffen and kre as contributors.

Yes, I know, I signed up for the list so that I could read the draft.

But there's no tm_stdoff, so it wasn't obvious that "gmtoff" and "stdoff" were referring to values in struct tm, and Brooks Harris said

> I just meant the values of gmtoff and stdoff are adjusted to satisfy Posix-time rather than reflect the values in the source files.

but tm_gmtoff is currently obviously not "adjusted to satisfy Posix-time" as, when tm_gmtoff was introduced, there was no tm_gmtoff in POSIX or, for that matter, in most UN*Xes (was it in *any* UN*Xes before tzcode put it in?), and it's also not "adjusted", it's just the current offset as calculated from the values in the source files.

And, as there's no "tm_stdoff" value even now, there's nothing *to* adjust about stdoff.