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Re: Daylight Saving
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From:
Yitzchak Scott-Thoennes
Date:
February 12, 2006 01:54
Subject:
Re: Daylight Saving
Message ID:
20060212095414.GD3260@efn.org
On Thu, Feb 09, 2006 at 12:05:42PM -0800, Bill Moseley wrote:
> 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?
>
> I kind of left this hanging.
>
> 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?
Yes, it's possible. I assume the timezone offset is the non-dst offset.
I'm not sure if Samoa uses US zipcodes :)
Offset dst flag Olson zone
-11 no US/Samoa or Pacific/Pago_Pago
-10 no HST or US/Hawaii or Pacific/Honolulu
-10 yes US/Aleutian or America/Adak
-9 yes US/Alaska or America/Anchorage
-8 yes PST8PDT or US/Pacific or America/Los_Angeles
-7 no MST or US/Arizona or America/Phoenix
-7 yes MST7MDT or US/Mountain or America/Denver
-6 yes CST6CDT or US/Central or America/Chicago
-5 no EST or US/East-Indiana or America/Indiana/Indianapolis
-5 yes EST5EDT or US/Eastern or America/New_York
I'm pretty sure the missing combinations of offset/dst flag don't
exist in the US. DateTime-TimeZone includes the first and third
columns of zone names; I'm not sure why it doesn't include those in
the second column.
For your amusement, the Olson files have this comment (among others) about
DST usage in the Falkland Islands:
# I know one lady there that keeps a list of which farm keeps DST and
# which doesn't each year. She runs a shop in Stanley, and says that
# the list changes each year. She uses it to communicate to her
# customers, catching them when they are home for lunch or dinner.
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