[tz] Ambiguous abbreviations for Australian timezones when daylight savings is in affect

Tim Parenti tim at timtimeonline.com
Tue Apr 2 19:32:08 UTC 2013

On 2 April 2013 14:38, Russ Allbery <rra at stanford.edu> wrote:

> That's actually one thing that the current abbreviations for Australia get
> right; they could be usable for indicating a time zone instead of an
> offset because they don't change with daylight saving time.

Yes, abbreviations that don't change with DST are nice... but only that.
Such abbreviations such as ET and PT are used frequently within the United
States in advertisements, newspapers, and general communication.  The
question of "What zone is meant by CT in this context?" is easily answered
with America/Chicago.

In Australia, the question then becomes, e.g., "What zone is meant by CST
in *this* context?"  That question is not so easily answered, if it is
answerable at all.  The case could be made that the user should be more
specific, but that defeats the purpose of using the abbreviations in the
first place.

Arizona in the United States provides an interesting study.  While some
"laymen" might consider their constant offset to "switch" between the
common notion of MT and PT, my (limited) experience with Arizona is that
most businesses and news outlets explicitly use the three-letter
abbreviation MST.

I don't think anyone's applying this argument to Australia (I'm certainly
not), but if we did, then Qld should use (A)EST while NSW/ACT/Vic/Tas use
(A)ET; NT should use (A)CST while SA uses (A)CT; WA could then simply use
(A)WT.  There are three issues with that:

   1. Abbreviations must be at least three characters to be
   POSIX-compliant, so the A becomes necessary for consistency.
   2. Using ACT to refer to Australian Central Time, which is not the time
   in the ACT (Australian Capital Territory), would be even more confusing
   than we have now.
   3. Unlike the United States, DST is the exception in Australia, not the

So it seems natural to instead emphasize the exception.  Arizona does this
by being explicit with the S in its abbreviation.  Australia can do this by
replacing the S with a D when appropriate.  This allows the humans using
the abbreviations to more easily use them for time conversion.

On 2 April 2013 14:25, John Hawkinson <jhawk at mit.edu> wrote:

> Two simple cases:
> (1) I look at the Date: header and I want to know, without thinking too
> hard, where the originator is.
> (2) I can't remember if we are in daylight time or standard time so
> I type "date" and look at the abbreviation.
> The current Australian abbrevs do a poor job of both of those cases.

I, too, like to be able to get a sense of what a timestamp means without
having to first think about what month it is, what season that means it is
"down under", which parts of which countries observe DST, and when those
DST changes just to determine an offset.  For programmatic purposes, this
is something computers do wonderfully with the help of tz, but when I get
an email on my phone, the last thing I want to do is find a terminal to
figure out what "09:00 Sydney time" means for me.

On 2 April 2013 14:25, John Hawkinson <jhawk at mit.edu> wrote:

> If they are worthless to software, let's
> make them useful to humans, please.

This is by far the most compelling argument I've seen yet, not just because
I happen to agree with it.

Tim Parenti
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