Re: [R] Automatic time zone conversion

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Tue 06 Dec 2005 - 01:45:13 EST

Note that even that will not reliably work on all platforms. The only values for the tz= argument that reliably work across platforms are tz = "" and tz = "GMT". (See RNews 4/1 Help Desk.) In fact, entering the above code into my machine

	> R.version.string  # Windows XP
	[1] "R version 2.2.0, 2005-10-24"

gives a different answer than on your machine:

	> as.POSIXct(as.character(strptime(cdate,format="%Y-%m-%d_%H:%M:%S")),
	+	tz="CST")+(8*3600)
	[1] "2000-05-11 08:00:00 CST"

Also if by CST you mean Central Standard Time as in Chicago, Houston and Winnipeg then its not 8 hours from GMT. See:

        http://www.stacken.kth.se/~kvickers/timezone.html

Could it be that you just want to read it in as GMT but display it in the current time zone? If so, try this:

	x <- as.POSIXct(chartr("_", " ", cdate), tz = "GMT")
	attr(x, "tzone") <- NULL


On 12/5/05, simon <sentientc@gmail.com> wrote:
> Dear R-help,
>
> I was trying to convert a date and time record extracted from a fortran
> subroutine I worte and I encounter some problem. The data read in time
> and date in a format like "2000-05-11_01:00:00.0000" in fortran output.
> It is in GMT. I need to convert it to CST (GMT+8). I did the following
> steps.
> > cdate
> [1] "2000-05-11_01:00:00.0000\005\003"
> # I am not sure why the extra characters at the end but it doesn't
> affect the strptime function so I just ingored it.
> > strptime(cdate,format="%Y-%m-%d_%H:%M:%S")
> [1] "2000-05-11 01:00:00"
> # In order to incoporate GMT into the record, I use paste function to
> stick it in.
> >as.POSIXct(as.character(strptime(cdate,format="%Y-%m-%d_%H:%M:%S")),tz="GMT")
> [1] "2000-05-11 01:00:00 GMT"
> #It is easier to just do a arthmatic to convert the timezone and ingore
> this attribute like
> >
> as.POSIXct(as.character(strptime(cdate,format="%Y-%m-%d_%H:%M:%S")),tz="CST")+(8*3600)
> [1] "2000-05-11 09:00:00 CST"
> I was wondering if there is a simpler method to do this.
>
> Thanks in advance,
>
> Simon
>
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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Dec 06 01:57:15 2005

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