Acronyms for Australian Time Zone Seasons

Robert Elz kre at munnari.OZ.AU
Thu Jan 25 07:22:13 UTC 2007

    Date:        Wed, 24 Jan 2007 14:06:23 +1100
    From:        "Sean B. Durkin" <sean at>
    Message-ID:  <45B6CD2F.2030100 at>

  | I wish to reopen the debate about the Australian Time Zone acronyms
  | (EST versus AEST versus EDT versus AEDT).

Do we really have to?   This debate happens over and over, and (for good
reason) nothing changes, so why waste time doing it again?

  | In the TZ database, the acronyms for the "Australian Eastern Standard Time"/
  | "Australian Eastern Daylight-Saving Time" time zone seasons is given as 
  | EST/EST.

There is no such thing as "daylight saving" time in Australia, Australia
has Summer Time, which is really quite intelligent on two levels.   First
because the very concept "daylight saving" is nonsense (not that that would
matter much by itself, and other countries certainly use that terminology)
and second, precisely because it makes the acronyms for the timezone be
unchanged, regardless of whether summer time is in force or not, which is
a *good* thing.

  | This page
  | shows that the Bureau of Meterology uses EST/EDT rather than EST/EST.

I am not quite sure I see the particular relevance of this, the Bureau of
Met do some things better than most people, but anything related to
time isn't one of them - time keeping isn't one of their tasks.

  | (1) PRACTICAL.
  | Even when the context of Australia is know, EST/EST makes it impractical
  | to record times in the local clock with the acronym.

No it doesn't, it is perfectly practical to record times this way.
What you mean, is that it is impractical to then attempt to invert
that recording, using the zone abbreviation to tell you the timezone
offset.   That's true, and that's good - about the one thing that
we usually do have fairly good agreement on that touches on this issue
is that using time zone name abbreviations for anything other than
display to users is a truly stupid thing to do (they're not unique,
half of them are simply invented by us with very little rationale, and
what's more, users can, and occasionally do, define their own for
whatever purpose they like).   From this I'd conclude that anything
that makes it more difficult for programmers to attempt to use the
abbreviation for anything other than display to users is a good thing,
and certainly not something we should be trying to "fix".

  | For example in an event is recorded in the Australia/Sydney time zone as
  | "2-Apr-2006 02:30 EST", and the context of "Australia" is given, what 
  | does this
  | mean? It is ambiguous. It could be taken to mean either:
  |   (a) 1-Apr-2006 15:30 GMT; or
  |   (b) 1-Apr-2006 16:30 GMT.

No, if you know it is Australia/Sydney you simply ignore the EST completely.
We know that summer time does not apply in Sydney in April (or more
precisely, did not in 2006, which is all that matters here), and that
consequently the timezone offset from UTC was 10 hours.  Thus 'b' must
be the correct answer to the question.

If you didn't know it was a Sydney timestamp, then you wouldn't have any
idea at all, the "EST" just isn't enough information by itself to achieve

If you used March 1st (or 2nd) instead of April, then again, if you knew
it was Sydney, you'd know it must have been Summer time, because in 2006
Summer time was in use in Sydney at the start of March.  And again, if you
don't know it was Sydney, you know nothing at all (worse here as the
problem is immediately obvious, as Brisbane would also be EST, and not
be Summer Time).

I know what you're suggesting is that if EDT was used, you'd know if it
was summer time or not, but that's only if you know it is Australia you're
talking about.  To make this kind of system generally applicable, we'd need
to have a worldwide unique set of timezone abbreviations, and some
authority to assign abbreviations to zones (worldwide) - much the same as
the ISO 3166 group does to the country name abbreviations (the group that
decided Australia should be AU and Austria should be AT).

That is, people would be told that they're required to use the abbreviations
assigned, rather than the ones they're used to - and for Australia, it
almost certainly couldn't be just EST (with or without an A on the front,
and with or without the D meaning Summer Time) - because Sumemr Time in
Tasmania is different than Summer time in the rest of the eastern states,
or has been in the past, and could be again - and if you're intending to
be able to use the abbreviation to uniquely identify a timezone, you're
going to have to have different ones for different zones.

Fortunately, it turns out that we don't need any such thing - or rather,
we already have exactly what we need, without authorities, and without
having to alter what users like to see - that is, if you want to be
unambiguous in a way that software can process the time string, and
generate the correct UTC equivalent, you just use +1000 or +1100 instead
of the alphabetic timezone.   It is easy, precise, and gives you exactly
what you're looking for,

  | I suggest that it would be better to have a pair of acronyms that could
  | be used to differentiate standard time from daylight saving time.

Why?   In general, that is exactly what we don't want to do, and is,
I suspect, exactly why the Australian legislators chose "Summer Time"
as the name for the "non standard" timezone - precisely so there was
no need to differentiate, it is simply "wallclock time" which is either
N, or N+1 hours offset from UTC (and yes, N can be fractional...)

  | The point that I am trying to make here
  | is the advantage of unambiguous acronyms just in the case where the time
  | zone is already known as Australia/Sydney.

In that case you're already done.   Once you know that, the abbreviation
isn't needed at all, the date and time are all that are required to let
you know whether standard time, or summer time, was in use.   Solved...
  | To be consistent with the treatment of other timezones, we should go
  | with the closest thing to the official acronym, rather than the most popular
  | one.

Actually, that's the precise opposite of the general goals of the tz
project, we mostly ignore "official" pronouncements, and stick with what
is actually used.

Further, that position actually defeats your purpose, as ...

  | I acknowledge that there is no legislatively official acronyms,

You're right, but there are legislatively official zone names, and in all
the Aust cases I've looked at (I haven't seen the ACT or Tas legislation),
the time during summer, from X to Y (which unfortunately keep changing...)
is known as "Summer Time".   In Vic the act of Parliament is even called
the "Summer Time Act", though not every state follows that convention.

If you read the recent WA bill, you'd even see that they refer to "Daylight
Saving" and stuff in the preamble, but then call it Summer Time when it
is defined.

It is Summer Time in NSW as well, and, I am fairly sure in South Aus.

The time, and argument to make, to the tz project, to get the acronyms
changed, would be when you can (reasonably) argue that the popular usage
in Australia is to use D instead of S for summer time, not when you can
find a single semi-govt web site (for a non-time based dept organisation
what's more) and say "well they use D, I like D, change to D please..."

  | It is not
  | too hard to extrapolate from their full spelling of the seasons
  | "Australian Eastern Standard Time" and "Australian Eastern Daylight Time",
  | that had their audience been more international, that they would have 
  | written the obvious acronyms AEST and AEDT.

You mean that we should do what they do, except when you don't like it,
then we should do what they obviously would do if they were thinking

The leading 'A' is a whole different issue to S/D debate.   However many
of the same arguments still apply - it isn't necessary, because the
abbreviations aren't useful anyway, and never need to be useful in the
way you seem to think they should be.

However, it is clear, that in an international context, we sometimes need
to make it clear what timezone we're talking about, and "Australian Eastern
Standard Time" is a reasonable way to do that, as is "United States
Eastern Standard Time" - once I would have said "North American Eastern 
Standard Time", but (even ignoring the oddball US counties) it isn't clear
(yet) that any such concept is going to remain - we don't know if Mexico
and (all) the Caribbean Islands are going to copy the new US rules.

But when it comes to the abbreviation, why would it be A for Australia?
Why wouldn't A mean any of the other countries whose name starts with A?
Australia is hardly unique that way...

When someone sees AEST, surely it would be reasonable for them to conclude
that means Standard Time in the UAE (which has AE as its country code).

Surely, if we're going to start throwing around country abbreviations
in timezone abbreviations, we should be using the generally accepted
abbreviation for the country, which for Australia, is certainly not an
unadorned A.   What's more, if we did decide we should do that, then we
should do it for all the timezone abbreviations, not just those in Aust.


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