[R] date conversion not as i would have expected

[Duncan Mackay]

Hi

This is on WinXP with regional settings as EST (we are now on DST but I run 
EST) R2.9.2

x <- structure(1254351600, class = c("POSIXt", "POSIXct"), tzone = "")
 > x
[1] "2009-10-01 09:00:00 EST"
 > as.POSIXlt(x)
[1] "2009-10-01 09:00:00 EST"
 > as.Date(x, formate="%Y-%m-%d" )
[1] "2009-09-30"

I had a similar problem last week. I am not sure how Bill Gates does his 
times but for R see Rnews 4(1).
There are slight differences between POSIX and Date classes

NB If you run EST in DST periods Bill Gates still gives the file stamp as 
DST in Vista and XP.
I would presume that it is the same for other zones where there is summer 
time zones

Regards

Duncan Mackay
Department of Agronomy and Soil Science
University of New England
ARMIDALE NSW 2351
Email: home: macka at northnet.com.au




At 00:51 22/10/2009, you wrote:
>Good day, i imported some data into R from Excel.  By using the edit()
>function, this is what one of the dates looks like in R:
>
> > x <- structure(1254351600, class = c("POSIXt", "POSIXct"), tzone = "")
>[1] "2009-10-01 BST"
>
>However, when i do the following, the date changes:
>
> > as.Date(x, formate="%Y-%m-%d" )
>[1] "2009-09-30"
>
>I don't understand why this is happening. I realise that i can get
>around this by doing as.Date(as.character(x)), but would be nice to
>understand why it doesn't work directly.
>
>C xx
>
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