[R] TimeZone Help - Finding TimeZone codes

Prof Brian Ripley ripley at stats.ox.ac.uk
Mon Nov 10 22:23:30 CET 2008

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 

> 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",
>       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
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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

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