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Re: Daylight Saving
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From:
Rick Measham
Date:
February 9, 2006 13:07
Subject:
Re: Daylight Saving
Message ID:
43EBAEC7.1000806@measham.id.au
> On Fri, Jan 20, 2006 at 07:26:16AM -0800, Bill Moseley wrote:
>>I have a zipcode table that lists the city, state, timezone offset
>>(eg -5) and a flag indicating if the location uses daylight saving
>>time for U.S. zipcodes. I don't have the Olson name in the table.
>>
>>How do I set the timezone in this case -- taking into
>>account the dst settings?
Bill Moseley then wrote:
> Is it possible to set a timezone on a DateTime object based on only
> the above information? Seems like one would need to know more (such
> as when Daylight Saving is in effect for that location. But, if so,
> could I see an example?
As you say, you don't know *when* the DST is in effect. I'm not sure
about the US, but two here, given PostCode 3030, the first '3' indicates
Victoria. There's only one TZ in Victoria therefore I can map any
postcode starting with a 3 to Australia/Melbourne
Does the US ever have more than one TZ per state? As you have the state
information, it wouldn't be hard to get a hash of states -> Olson Time
Zone names. If you have more than one TZ per state, I'd have to assume
its rare and so you could do those states by hand (painful I know, but I
imagine there's a ZIP <-> lat/lon table around that would help you
divide the state into positive regions
(http://www.zipinfo.com/search/zipcode.htm). After that you can hand-cut
those along the edges of those regions.
Just a few thoughts
Cheers!
Rick Measham
--
"War is God's way of teaching Americans geography."
-- Ambrose Bierce
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