[R] TimeZone Help - Finding TimeZone codes

[hadley wickham]

On Thu, Nov 13, 2008 at 9:10 PM, J Dougherty <jwd at surewest.net> wrote:
> On Monday 10 November 2008 01:23:30 pm Prof Brian Ripley wrote:
>> See ?Sys.timezone, which help.search("timezone") points you to.
>>
>> On Mon, 10 Nov 2008, stephen sefick wrote:
>> > I have looked at
>> > ?as.POSIXct
>>
>> That also links to Sys.timezone from the 'tz' argument.
>>
>> > ?POSIXct
>> > and many of the references that are on those pages.
>> >
>> > I am bewildered with timezones.  Is there a way to get what would go
>> > into tz="" for making a function that uses POSIXct to be able to be
>> > used in all of the timezones in just the united states?  This is for
>> > both windows and mac...
>>
>> There are rather a lot of timezones in the United States (sic), down to
>> individual counties.
>>
> There are six: Eastern Standard (UTC-5), Central Standard (UTC-6), Mountain
> Standard (UTC-7), Pacific Standard (UTC-8), Alaskan (UTC-9) and Hawaiian-
> Aleutian (UTC-10).  Daylight Savings Time, a stupid institution, is not
> observed by a sizeable piece of Arizona (most of the state, though apparently
> the Navaho DO observe it, while the Hopi do not) and Hawaii.

There maybe six at the moment, but timezones also have to work in the
past.  Time zone rules have changed many times in many different
places, and so, as Brian mentioned, time zone data often goes down to
the county level.

Hadley

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