R help - Nov 2008 - TimeZone Help - Finding TimeZone codes

I have looked at
?as.POSIXct
?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...
this is the function that I am wanting to use it with

library(maptools)
sunrise.set <- function(lat, long, date, timezone="UTC",
num.days=1){
       #this needs to be long lat#
       lat.long <- matrix(c(long, lat), nrow=1)
       day <- as.POSIXct(date, tz=timezone)
       sequence <- seq(from=day, length.out=num.days , by="days")
       sunrise <- sunriset(lat.long, sequence, direction="sunrise",
POSIXct=TRUE)
       sunset <- sunriset(lat.long, sequence, direction="sunset",
POSIXct=TRUE)
       ss <- data.frame(sunrise, sunset)
       ss <- ss[,-c(1,3)]
       colnames(ss)<-c("sunrise", "sunset")
       return(ss)
 }



thanks in advance,

-- 
Stephen Sefick
Research Scientist
Southeastern Natural Sciences Academy

Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods.  We are mammals, and have not exhausted the
annoying little problems of being mammals.

								-K. Mullis

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.

For both Windows (sic) and Mac OS (sic) R uses the Olsen database, and so 
timezones are best specfied by "America/<city name>" for city
names, plus
"America/Kentucky/{Louisville,Monticello}"

> this is the function that I am wanting to use it with
>
> library(maptools)
> sunrise.set <- function(lat, long, date, timezone="UTC",
num.days=1){
>       #this needs to be long lat#
>       lat.long <- matrix(c(long, lat), nrow=1)
>       day <- as.POSIXct(date, tz=timezone)
>       sequence <- seq(from=day, length.out=num.days ,
by="days")
>       sunrise <- sunriset(lat.long, sequence,
direction="sunrise",
> POSIXct=TRUE)
>       sunset <- sunriset(lat.long, sequence,
direction="sunset", POSIXct=TRUE)
>       ss <- data.frame(sunrise, sunset)
>       ss <- ss[,-c(1,3)]
>       colnames(ss)<-c("sunrise", "sunset")
>       return(ss)
> }
>
>
>
> thanks in advance,
>
> -- 
> Stephen Sefick
> Research Scientist
> Southeastern Natural Sciences Academy
>
> Let's not spend our time and resources thinking about things that are
> so little or so large that all they really do for us is puff us up and
> make us feel like gods.  We are mammals, and have not exhausted the
> annoying little problems of being mammals.
>
> 								-K. Mullis
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595