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

[Guy Harris]

On Jan 6, 2024, at 12:31 PM, Paul Eggert via tz <tz at iana.org> wrote:

> On 2024-01-06 09:55, Brooks Harris via tz wrote:
> 
>> in many situations, such as STDOFF shifts, STDOFF shifts simultaneous with DST shifts, or "double summertime" the TzIf values are essentially 'lying'
> 
> Surely this goes too far. Whether a particular UT offset is "standard time" or "daylight saving time" (or something else) does not concern ordinary users and is pretty much arbitrary - as witness the disagreement over whether Morocco observes "standard time" or "daylight saving time" for most of the year. To this end, the TZif values are not lying; they're merely limiting themselves to the info needed to display timestamps.

It appears, from some comments here (emails from Brooks Harris and Michael H Deckers), that the values of STDOFF and SAVE, and not just the current offset from UTC, matter to at least some users.

It would help if they indicated the situations in which STDOFF and SAVE matter and gave examples of software that uses them.