pytz has so many timezones!

[mensanator at aol.com]

On Oct 8, 3:27 pm, "Chris Mellon" <arka... at gmail.com> wrote:
> On 10/8/07, mensana... at aol.com <mensana... at aol.com> wrote:
>
>
>
>
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> > On Oct 8, 1:00 pm, "J. Clifford Dyer" <j... at sdf.lonestar.org> wrote:
> > > On Mon, Oct 08, 2007 at 10:41:03AM -0700, mensana... at aol.com wrote regarding Re: pytz has so many timezones!:
>
> > > > On Oct 8, 2:32 am, Sanjay <skpate... at gmail.com> wrote:
> > > > > Hi All,
>
> > > > > I am using pytz.common_timezones to populate the timezone combo box of
> > > > > some user registration form. But as it has so many timezones (around
> > > > > 400),
>
> > > > There are only 25 timezones: -12, -11, ... -1, 0 (GMT), +1, ... +11,
> > > > +12.
>
> > > > A handful of countries set their clocks offset by a half hour,
> > > > but those aren't timezones.
>
> > > I'm sorry.  By what even vaguely useful definition of "Timezone" is it not a timezone if it's offset by half an hour?
>
> > The miltary doesn't recognize them as timezones. They'll make
> > a not that the local time observed doesn't match the timezone,
> > but they don't call it a seperate timezone.
>
> What do you mean by "the military" and why do you think they're
> authoritative on the topic of timezones?

Because they publish maps?

> The US timekeeping authority
> is a branch of the US Navy,

Isn't that "the military"?

> but as far as I know they don't define timezones.

Ok, maybe they don't define them. But they get them from somewhere
and the zones are labeled A-Z (don't ask which letter isn't used).
Zone Z is equivalent to GMT and the time is refered to as Zulu time.

That's 25 zones, not 400. Under that system there are no half-hour
offset zones, no zones based on sunset and no lunatic GMT+13 zones.

You'll never learn to run without first learning how to walk.

>
>
>
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> > > > The 400 you're seeing are duplications based on locality. Of the 86
> > > > shown in Windows, all but 33 are dulplicate references to the same
> > > > timezones.
>
> > > > For example, Windows has seperate listings for
>
> > > > Central America
> > > > Central Time (US & Canada)
> > > > Guadalahara, Mexico City, Monterry - New
> > > > Guadalahara, Mexico City, Monterry - Old
> > > > Saskatchewan
>
> > > > but they are all GMT-6
>
> > > Those are non-duplicate (and perhaps inaccurate, I'm not sure).  US time switches from standard to Daylight Savings earlier than Mexico, and switches back later, as of this year.
>
> > Duplicate timezones doesn't mean duplicate time,
> > as you point out. Does the OP want to know the truth
> > or does he want to know something he can understand.
>
> > > Reducing them to a single time zone will result in aberrant functionality in one or more locales.
>
> > I would hardly think that's an issue on the user registration
> > form the OP is trying to create.
>
> It's not clear at all from the OPs post exactly what functionality he
> is trying to derive from the timezone.

Yep, we can't read his mind.

> Since timezones (obviously)
> contain more information than just the GMT offset

Of course. But the GMT offset could be used to filter his list
of 400 choices, couldn't it?

> (otherwise we
> wouldn't even have them), he may very well want to use the timezone
> given by the user to display correct local time to them. In this case,
> the actual, correct, political timezone is important, not just the GMT
> offset.

Agreed. But if someone gave me a list of 400 choices, I would look
for some way to reduce the list to a manageable choice. Isn't that
what the OP wants?

Why not teach him the truth, starting from the top level? Shouldn't
you teach him to fish rather than just give him one?

>
> > > Cheers,
> > > Cliff
>
> > --
> >http://mail.python.org/mailman/listinfo/python-list