[tz] Reason for removal of several TZ

[Derick Rethans]

On Sun, 3 Dec 2017, Paul Eggert wrote:

> Thomas M Steenholdt wrote:
> >  From what I've seen, PHP (on Ubuntu) had some hiccups and started
> > mentioning Sao Paolo in my date/time outputs, because WGT/WGST was
> > suddenly missing:
> 
> As I understand from
> <https://bugs.launchpad.net/ubuntu/+source/tzdata/+bug/1734967>, PHP attempts
> to guess the tzdb Zone name (e.g., "Europe/Berlin") from the abbreviation and
> UT offset, which is the sort of thing that we have long explicitly warned
> should not be done because abbreviations are ambiguous.

PHP does not guess tzdb names from abbreviations/UT offsets by default, 
it hasn't since 2011 (PHP 5.5): 
https://github.com/php/php-src/commit/37d1038958a6442de8f559a443f117c6ae1c2d78

There are still functions to guess the timezone from abbreviation + 
offset, but that is a developers choice: 
http://php.net/manual/en/function.timezone-name-from-abbr.php I'll go 
add a warning to the docs defining it as "deprecated".

Input routines (strtotime()) also still allow the use of abbreviations 
where they are defined in tzdata, in which case the are statically 
mapped to tzdb names: 
https://github.com/php/php-src/blob/master/ext/date/lib/fallbackmap.h — 
which has not changed to keep backwards compatibility (VET is still 
wrong in it, for example). 

cheers,
Derick