similar to: as.POSIXct Bug when used with POSIXlt arg and tz= arg (PR#3646)

Can anyone please shed any light on why R DateTimeClasses give weird times for when daylight saving time information changes, and which aren't consistent with the OS? Example: Expected result: in New Zealand DST stopped (NZDT -> NZST) at 03:00 NZDT on 2010-04-04, as confirmed by the OS time zone info (OS X 10.8.2): zdump -v /etc/localtime /etc/localtime Sat Apr 3 13:59:59 2010 UTC

R-devel: Some very inconsistent behavior, that I can't seem to find documented. Sys.setenv(TZ="GMT") str(unclass(strptime("1969-12-31 23:59:59","%Y-%m-%d %H:%M:%S"))) List of 9 $ sec : num 59 $ min : int 59 $ hour : int 23 $ mday : int 31 $ mon : int 11 $ year : int 69 $ wday : int 3 $ yday : int 364 $ isdst: int 0 - attr(*, "tzone")= chr

This is not a bug in R: the documentation does say the result is OS-specific. `GMT' is a not a proper timezone on Windows, so NA is a valid answer. (Windows seems to use GMT to refer to the timezone of the UK, e.g. > Sys.time() [1] "2005-07-11 07:49:56 GMT Daylight Time" > Sys.timezone() [1] "GMT Daylight Time" although I am in British Summer Time not GMT.)

Bumping this up to the front again ... because it exhibits a difference in behaviour of R across OSs. Such a 'feature' may not be desirable. On 4 April 2016 at 18:00, Arunkumar Srinivasan wrote: | Hello, | | Following Dirk's post here: https://github.com/Rdatatable/data.table/issues/1619 | we would like to clarify if this is the right behaviour, and if so, | the rationale behind it.

I have a data frame that contains dates, but when I use as.POSIXlt() I lose the hours on all records. I traced this down to a particuar hour which causes the issue... > as.POSIXlt('2004-10-31 02:00:00') [1] "2004-10-31" > as.POSIXlt('2004-10-31 03:00:00') [1] "2004-10-31 03:00:00" How do I tell as.POSIXlt() to ignore daylight savings and just convert to

?Hi again, I take advantage of my previous mail to ask you a question for which I was looking for an answer when detected the behaviour I previously told. In the help of DataTimeClasses one can read: "POSIXlt" objects will often have an attribute "tzone", a character vector of length 3 giving the time zone name from the TZ environment variable and the names of the base time

Hello, Following Dirk's post here: https://github.com/Rdatatable/data.table/issues/1619 we would like to clarify if this is the right behaviour, and if so, the rationale behind it. Here's the summary (thanks to Dirk and Joshua): Sys.setenv("TZ"="America/Chicago") dates = as.Date("2016-03-02") + (0:3)*7 # four Wednesdays # [1] "2016-03-02"

Hello, Suppose we need a function that takes a POSIXct object and need to calculate the time difference between it and GMT time: gmtDiff <- function(time) { time.gmt <- as.POSIXct(format(time, tz="GMT")) time.plt <- as.POSIXlt(time) dlstime <- ifelse(time.plt$isdst > 0, 1, 0) timezone <- as.numeric(difftime(time, time.gmt, units="hours"))

tplate at acm.org wrote: > Running under Windows XP 64 bit, as.POSIXlt()/as.POSIXct() seem > to think that US time zones (EST5EDT, MST7MDT) switched from daylight > savings back to standard time on Oct 28, 2007, whereas the switch > is actually on Sun Nov 04, 2007. > > =20 Not Our Problem. (This sort of thing never is. We are wholly dependent=20 on the OS for this information).

I have found what looks like a small problem in trunc.POSIXt() involving the transition to/from standard time and daylight savings time. Assuming my assessment is correct, I have a potential solution to offer. If a time in daylight savings time is rounded such that the rounded value is on the other side of the transition, the isdst element does not get changed accordingly. I have tested only

Tracking down this bug was joint work with Jermoe Asselin (jerome at hivnet.ubc.ca) and Patrick Connolly (p.connolly at hortresearch.co.nz). We collectively were able to determine that this is a problem in Windows 2000 but not in Linux. Timezones of the form GMT-5, GMT+3, etc. do not work properly in Windows 2000 for nearby dates in daylight savings time although they do work for nearby dates

Running under Windows XP 64 bit, as.POSIXlt()/as.POSIXct() seem to think that US time zones (EST5EDT, MST7MDT) switched from daylight savings back to standard time on Oct 28, 2007, whereas the switch is actually on Sun Nov 04, 2007. Examples: > Sys.timezone() [1] "Mountain Daylight Time" > as.POSIXct("2007-10-30 12:38:47") [1] "2007-10-30 12:38:47 Mountain

> On 18 May 2017, at 14:51, peter dalgaard <pdalgd at gmail.com> wrote: > > >> On 18 May 2017, at 13:47 , Joris Meys <jorismeys at gmail.com> wrote: >> >> Correction: Also dlt uses the default timezone, but POSIXlt is not recalculated whereas POSIXct is. Reason for that is the different way values are stored (hours, minutes, seconds as opposed to minutes

I'm having difficulties with daylight saving times in US time zones. (Apologies for the long post, but the problem seems subtle and complex, unless I'm doing something completely wrong, in which case it should be evident from the first 10 lines below.) This is what I see, using a (slightly modified) example from ?as.POSIXlt : > as.POSIXlt((d <- Sys.time()), "EST5EDT") #

Correction: Also dlt uses the default timezone, but POSIXlt is not recalculated whereas POSIXct is. Reason for that is the different way values are stored (hours, minutes, seconds as opposed to minutes from origin, as explained in my previous mail) CHeers Joris On Thu, May 18, 2017 at 1:45 PM, Joris Meys <jorismeys at gmail.com> wrote: > This has to do with your own timezone. If I run

> On 18 May 2017, at 11:00 , Patrick Connolly <p_connolly at slingshot.co.nz> wrote: > > On Wed, 17-May-2017 at 01:21PM +0200, Peter Dalgaard wrote: > > |> > |> Anyways, you might want to > |> > |> a) move the discussion to R-devel > |> b) include your platform (hardware, OS) and time zone info > > System: Host: MTA-V1-427894 Kernel:

Dear all, I have just detected what seems a minor inconsistence with data types. If one unlists a POSIXlt time with GMT zone gets a numeric vector, since the POSIXlt list has no `zone` element, while if one unlists a POSIXlt time with a non GMT zone (also non specifying tz if the Sys.timezone is not GMT) gets a character vector due to including the `zone` element. > x <-

Full_Name: Erich Neuwirth Version: 2.3.1 OS: Windows XP, Linux Submission from: (NULL) (131.130.135.167) Converting Sys.Date() to a POSIX compliant time type in different ways produces inconsistent results: > Sys.date() [1] "2006-09-01" > as.POSIXct(Sys.Date()) [1] "2006-09-01 02:00:00 CEST" > as.POSIXlt(Sys.Date()) [1] "2006-09-01" >

> On 18 May 2017, at 14:58 , Martyn Plummer <plummerM at iarc.fr> wrote: > > > >> On 18 May 2017, at 14:51, peter dalgaard <pdalgd at gmail.com> wrote: >> >> >>> On 18 May 2017, at 13:47 , Joris Meys <jorismeys at gmail.com> wrote: >>> >>> Correction: Also dlt uses the default timezone, but POSIXlt is not recalculated

Uwe Ligges wrote: > Consider the following data.frame: > > > testdata > date nothing > 1 1991-12-31 NA > 2 1991-12-31 NA > > where date is of class POSIXlt. For easy reproducibility: > > "testdata" <- structure(list(date = structure(list(sec = c(0, 0), > min = c(0, 0), hour = c(0, 0), mday = c(31, 31), mon = c(11, 11),