[R] POSIXct bug?

[Martin Maechler]

>>>>> "Spencer" == Spencer Graves <spencer.graves at pdf.com>
>>>>>     on Sun, 27 Feb 2005 07:15:44 -0800 writes:

    Spencer> Hi, Gabor: Of course: time zone vs. GMT.

    Spencer>        Next question: Might a simple example that
    Spencer> illustrates this be added to the help file for
    Spencer> "as.POSIXct", and if yes, what should be done to
    Spencer> make that happen?

send such a simple example {few lines of R code + comments ("# ...")}
to R-devel (or to an R-core member you know who would take it up).

Martin

    Spencer> Gabor Grothendieck wrote:

    >> Spencer Graves <spencer.graves <at> pdf.com> writes:
    >> 
    >> : 
    >> : In R 2.0.1 under Windows 2000, at least in some cases, as.POSIXct 
    >> : adds one to the date: 
    >> : 
    >> :  > March1.1959.POSIXct <- as.POSIXct("1959-03-01")
    >> :  > March1.1959.POSIXlt <- as.POSIXlt("1959-03-01")
    >> :  >
    >> :  > (Mar2.59 <- as.Date(March1.1959.POSIXct))
    >> : [1] "1959-03-02"
    >> :  > as.Date(March1.1959.POSIXlt)
    >> : [1] "1959-03-01"
    >> :  >
    >> :  > as.Date(as.POSIXct(Mar2.59))
    >> : [1] "1959-03-02"
    >> :  > as.Date(as.POSIXct(as.character(Mar2.59)))
    >> : [1] "1959-03-03"
    >> :  > print(POSIX.i <- as.POSIXct("1959-03-01"))
    >> : [1] "1959-03-01 Pacific Standard Time"
    >> :  > for(i in 1:11){
    >> : +   print(date.i <- as.Date(POSIX.i))
    >> : +   print(POSIX.i <- as.POSIXct(as.character(date.i)))
    >> : + }
    >> : [1] "1959-03-02"
    >> : [1] "1959-03-02 Pacific Standard Time"
    >> : [1] "1959-03-03"
    >> : [1] "1959-03-03 Pacific Standard Time"
    >> : [1] "1959-03-04"
    >> : [1] "1959-03-04 Pacific Standard Time"
    >> : [1] "1959-03-05"
    >> : [1] "1959-03-05 Pacific Standard Time"
    >> : [1] "1959-03-06"
    >> : [1] "1959-03-06 Pacific Standard Time"
    >> : [1] "1959-03-07"
    >> : [1] "1959-03-07 Pacific Standard Time"
    >> : [1] "1959-03-08"
    >> : [1] "1959-03-08 Pacific Standard Time"
    >> : [1] "1959-03-09"
    >> : [1] "1959-03-09 Pacific Standard Time"
    >> : [1] "1959-03-10"
    >> : [1] "1959-03-10 Pacific Standard Time"
    >> : [1] "1959-03-11"
    >> : [1] "1959-03-11 Pacific Standard Time"
    >> : [1] "1959-03-12"
    >> : [1] "1959-03-12 Pacific Standard Time"
    >> :  >      
    >> :       Comments?
    >> 
    >> I am not sure that the code really speaks for itself.  What is the bug?
    >> Note that as.Date converts dates relative to GMT, not the current time
    >> zone.  If you want to convert a POSIXct date to a Date date relative
    >> to the current timezone you can convert it to character first.  RNews 4/1
    >> has a table that provides a number of such idioms.