Re: Time zone names (was REMINDER: CharMod Call Today)

This subject is not worth belaboring, but I'll make a few comments.

Mark
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----- Original Message ----- 
From: "Jungshik Shin" <[email protected]>
To: "Mark Davis" <[email protected]>
Cc: <[email protected]>; <[email protected]>; <[email protected]>; "icu-list"
<[email protected]>
Sent: Mon, 2003 Dec 08 10:04
Subject: Re: Time zone names (was REMINDER: CharMod Call Today)


>
>
> On Mon, 8 Dec 2003, Mark Davis wrote:
>
> > have a meeting "Tuesdays at 10:00 PT" (Pacific Time), that carries more (and
> > different) information than saying "Tuesdays at 10:00 GMT-08:00". For part
of
> > the year -- as a matter of fact, for a *majority* of the year -- it is
> > "Tuesdays at 10:00 GMT-07:00". The problem is that you have to go look up
> >  against the
>
>   Well, that's why I speficically say US PST with 'S'. If this had been
> when the daylight saving time is in effect, I would have written 'US PDT'.
> Needless to say, always using UTC is clear and unambigous. If the wall
> clock time is to be used, it can be followed by 'UTC -0800 (US PST)'
> or 'UTC -0700 (US PDT)'. 'US PDT' is enclosed by parentheses because
> I believe that should only be 'parenthetical'. I wouldn't expect any
> 'layperson' on the street to do that, but this is on I18N list.

You are missing the point "Tuesdays at 10:00 PT" is not simply equivalent to
"'UTC -0800 (US PST)'
or 'UTC -0700 (US PDT)'". It is equivalent to "'UTC -0700 between the dates when
the US is on Daylight Time and UTC -0800 otherwise.


"Tuesdays at 10:00
>
>
> > What would truely be useful would be if all those countries of the world
that
> > use summer time could standardize on two dates during the year to switch
their
> > clocks (e.g. 3th Sundays in March and September, near the æquinoctia). Then
you
>
>   Obviously, that doesn't work even if we put aside arising from
> different climates in different regions in the _same_ hemisphere because
> there are two hemisphers in a sphere :-)

Yes it does, see below. Where observed, daylight savings in the north shifts an
hour east in the northern hemisphere's summer, typically starting somewhere
around the March equinox, and and shifts back somewhere around the September
equinox. In the south, it shifts an hour east typically starting somewhere
around the September equinox, and and shifts back somewhere around the March
equinox. These could, as a matter of fact, be the same days worldwide, if there
were the will to do so.

(Of course, I don't expect anything like this to ever happen; there is a great
deal of inertia in these matters. After all, nowhere in the world is truely on
the metric system yet: the US not for distance and other measures, and the whole
world not for time.)

>
> > could use three appreviations to fully specify the time without needing
> > to know detailed daylight conventions:
>
>   I'm not sure what you meant by 'three appreviations'. Did you mean
> things like PST, EST, JST, and BST? I don't think using them is a good
> idea in any way except as an aid to 'humans'.

What I mean by the three abbreviations are the three abbreviations that
(surprise) I actually listed, immediately below writing that. If there were a
consistent "switch-over" date, then for any location you could specify and
communicate precisely what its wall time was, with one of the three notations
given below.

>
>
> > - Tuesdays at 10:00 GMT-08:00 = constant offset -08:00 from GMT
> > - Tuesdays at 10:00 GMT-08:00N = GMT-08:00 from Sept-March, GMT-07:00 from
> > March-Sept
> > - Tuesdays at 10:00 GMT-08:00S = GMT-08:00 from March-Sept, GMT-07:00 from
> > Sept-March
> >
> > (Cross-posting to the ICU list, since there was a recent discussion of
timezones
> > there.)
>
>   Is there any reason you stick to GMT (that got obsoleted/abolished a
> long long time ago) instead of UTC? I also filed a bug on ICU on this
> issue a long time ago, but haven't heard back.

Because in normal usage, GMT and UTC are interchangeable.

>
>   Jungshik
>
>