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Re: More time zones

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: Thomas Lockhart <lockhart(at)fourpalms(dot)org>
Cc: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>,Thomas Lockhart <thomas(at)fourpalms(dot)org>,PostgreSQL Hackers List <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: More time zones
Date: 2002-02-26 03:04:52
Message-ID: Pine.LNX.4.30.0202252149380.836-100000@peter.localdomain (view raw or flat)
Thread:
Lists: pgsql-hackers
Thomas Lockhart writes:

> > I claim that most of the time zone abbreviations that we have now are
> > purely theoretical fabrications.
>
> Hmm. How would you arrive at that conclusion?

Some of the entries are obviously bogus, for example BRA "Brazil Time",
although Brazil has three time zones.  Also, there are only half a dozen
or so countries in the world that have more than one time zone, and quite
a few countries don't speak English, so it seems unlikely that in a place
like that a common-usage English-language time zone designation would
evolve.  So for instance, FWT "French Winter Time" is highly unlikely to
be in actual use.

> Most of the existing entries appear in the zinc database and in other
> references, and I'll assume that most of the places which these
> correspond to actually exist.

The tz database contains this note:

"""
Alphabetic time zone abbreviations should not be used as unique
identifiers for UTC offsets as they are ambiguous in practice. For
example, "EST" denotes 5 hours behind UTC in English-speaking North
America, but it denotes 10 or 11 hours ahead of UTC in Australia; and
French-speaking North Americans prefer "HNE" to "EST". For compatibility
with POSIX the tz database contains English abbreviations for all time
stamps but in many cases these are merely inventions of the database
maintainers.
"""

So what this means is that the tz database (which I assume is the same as
the zinc you speak of) merely assigns some string to each distinct set of
rules so that POSIX systems have something to put into their tzname
variable.

One concern I have about the time zone abbreviation database is that the
inflation of possible choices makes any kind of error checking mostly
non-existant.  And who is going to remember all the abbreviations anyway,
even if they were documented?

I think we should scrap about 90% of the time zone names we have in there
unless there's evidence of actual use.  Instead, it would be preferrable
to use numerical offsets, or if some geographical association is desired,
the Continent/City syntax.

-- 
Peter Eisentraut   peter_e(at)gmx(dot)net


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