[tz] More on EU/UK/Brexit clock changes

[Michael H Deckers]

    On 2020-02-12 01:57, Paul Eggert wrote about the
    study from the House of (Time) Lords:

> On 2/11/20 5:36 PM, Chris Woodbury wrote:
>> The "Time Lords" subcommittee has released yet another study.  Find 
>> it at:
>>
>> https://publications.parliament.uk/pa/ld5801/ldselect/ldeucom/15/15.pdf
    ...
> They also mentioned us at some length on page 25 about how to best 
> implement UTC+1 year-round in the UK.


    In the IANA statement SCT0004 referenced on page 22,
    I read:

      >>  The notion of permanent summertime is not supported by the 
POSIX.1-2017
      >>  standard[4], which covers most of the computer servers in the UK.

    This is correct in the sense that POSIX does not mention
    summer time -- but POSIX mentions
      "alternative (dst - such as Daylight Savings Time) timezone"
    in addition to standard time.

    And a TZ string may well specify that the "alternative" time
    is "permanent" (in the sense of being in force throughout the
    year), for instance with:
                        EET-2/BST-1,J1/01:00,J365/24:00
    so that POSIX does support permanent "alternative time zones".

    Hence it is not clear to me exactly which unsupported feature
    of POSIX is meant in the quote above.

    Michael Deckers.