[tz] [PROPOSED] Avoid backward links in zone.tab
Michael H Deckers
michael.h.deckers at googlemail.com
Mon May 10 10:43:56 UTC 2021
On 2021-05-10 08:38, Paul Eggert wrote:
>
> The idea is to move Zones into 'backward' if they're identical to some
> other Zone after 1970.
If these rules really hold for backzone (are
they listed anywhere?), then
America/Curacao
also should go to backzone, and one of
Africa/Johannesburg and Africa/Maputo
and three of
Pacific/Majuro, Pacific/Tarawa,
Pacific/Funafuti, Pacific/Mata-Utu
should go to backzone.
By the way, do these rules imply that
Pacific/Yap
with the data as of 2005k belongs to backzone?
A remark on backward compatibility:
The proposed change is not conservative in the sense that
information that could automatically be extracted from
previous versions is no longer available in this way.
To wit:
It is no longer possible to automatically find geographical
coordinates for the tzdb timezones described in backzone.
In previous versions, the name of a tzdb timezone in
backzone could also be found in zone.tab together with
its country code and the coordinates for its location
(except for backzone/Asia/Hanoi).
After the change, there is no systematic way to find
the right line in zone.tab with the coordinates, even
if one supposes that one can automatically deduce the
ISO country code for the name of a tzdb timezone in
backzone (which is quite tricky and not so simple as
in previous versions). Only the comment entry in a
line of zone.tab (such as "Vietnam (south)") gives
some indication on the name of the timezone (eg,
Asia/Ho_Chi_Minh) whose geographic coordinates
are contained in that line.
I am aware that zone.tab is deprecated, so that
one could say that the previously possible method was
not guaranteed to work across versions -- but then the
locations for backzone timezones could be omitted or put
somewhere where they can be found automatically.
Michael Deckers.
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