From ggrothendieck at gmail.com  Fri Mar  3 20:03:42 2006
From: ggrothendieck at gmail.com (Gabor Grothendieck)
Date: Fri, 3 Mar 2006 14:03:42 -0500
Subject: [Rd] [as.POSIXlt]: Incorrect conversion only for some specific
	date/time (PR#8654)
In-Reply-To: <20060303185500.750B1103F0@slim.kubism.ku.dk>
References: <20060303185500.750B1103F0@slim.kubism.ku.dk>
Message-ID: <971536df0603031103w2b5ad68dwa636ae094d0aa934@mail.gmail.com>

Its due to daylight savings time in your time zone.  If you don't want
that then use the tz = "GMT" argument to specify GMT time zone as
GMT has no daylight savings time or set your entire session that way,
i.e. Sys.putenv(TZ = "GMT").

Also read the Help Desk article in R News 4/1 on dates and times.

On 3/3/06, aziz.chaouch at gmail.com <aziz.chaouch at gmail.com> wrote:
> Full_Name: Aziz Chaouch
> Version: 2.2.1
> OS: XP/2000
> Submission from: (NULL) (132.156.89.240)
>
>
> Hi,
>
> I'm not sure this is a "bug" but here is the problem:
>
> I'm using the function as.POSIXlt to convert character strings into time
> objects. I'm using date format as "YYYY/M/D HH:MM" such as as.POSIXlt("1999/6/7
> 13:30"). Most of the time, this works fine. However for some reasons, some
> specific dates such as "2000/4/2 02:00" are not correctly converted with respect
> to hours (the converted hour is 01:00 while the input was 02:00). Look for the
> result in R:
>
> > as.POSIXlt("2000/4/2 02:00")
> [1] "2000-04-02 01:00:00"
>
> Strangely, other hours are converted correctly:
>
> > as.POSIXlt("2000/4/2 01:00")
> [1] "2000-04-02 01:00:00"
> > as.POSIXlt("2000/4/2 03:00")
> [1] "2000-04-02 03:00:00"
>
> I've only experienced this problem for some specific dates when the time is set
> to 02:00.
>
> The following list shows date/time that have problems so far but obviously there
> are more:
> "2000/4/2 02:00"
> "2001/4/1 02:00"
> "2002/4/7 02:00"
> "2003/4/6 02:00"
> "2004/4/4 02:00"
> "2005/4/3 02:00"
>
> Does anybody knows what's the problem? Am I missing something?
>
> Thanks
>
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>



[Rd] [as.POSIXlt]: Incorrect conversion only for some specific date/time (PR#8654)
Gabor Grothendieck