[Rd] R4.1: seq.POSIXt, tz="AEST" (PR#9572)

Mon Mar 19 14:58:50 CET 2007

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I am sorry, "AEST" was wrong. I can't work out what timezone code it is, but
my default timezone here in eastern australia prints as:
> as.POSIXct("1970-01-01", tz="")
[1] "1970-01-01 AUS Eastern Daylight Time"

and that is the one that has repeated dates before 1970.

But I take your point that it is fundamentally a problem with Windows.

--Felix

On 3/19/07, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
>
> Hmm, AEST is not a valid time zone on Windows.
> See ?as.POSIXlt for one of several places where this is documented.
>
> But in any case, the underlying problem is in the OS, and we only try to
> work around it to the best of our knowledge (and that excludes
> undocumented time zones).
>
>
> On Mon, 19 Mar 2007, felix at nfrac.org wrote:
>
> > Times from seq.POSIXt come out wrong in AEST timezone around Feb 29
> every
> > leap year before 1970 (on Windows XP).
> >
> > According to help(DateTimeClasses), this is handled by "our own C code".
> >
> >> x <- as.POSIXct("1968-02-27") # tz="AEST"
> >> x.gmt <- as.POSIXct("1968-02-27", tz="GMT")
> >> data.frame(
> >     GMT=seq(x.gmt, by="day", length=8),
> >     byday=seq(x, by="day", length=8),
> >     byDST=seq(x, by="DSTday", length=8))
> >         GMT      byday      byDST
> > 1 1968-02-27 1968-02-27 1968-02-27
> > 2 1968-02-28 1968-02-28 1968-02-28
> > 3 1968-02-29 1968-03-01 1968-03-02
> > 4 1968-03-01 1968-03-02 1968-03-02
> > 5 1968-03-02 1968-03-02 1968-03-02
> > 6 1968-03-03 1968-03-03 1968-03-03
> > 7 1968-03-04 1968-03-04 1968-03-04
> > 8 1968-03-05 1968-03-05 1968-03-05
> >
> >> R.version
> >               _
> > platform       i386-pc-mingw32
> > arch           i386
> > os             mingw32
> > system         i386, mingw32
> > status
> > major          2
> > minor          4.1
> > year           2006
> > month          12
> > day            18
> > svn rev        40228
> > language       R
> > version.string R version 2.4.1 (2006-12-18)
> >
> >
> >
> >
>
> --
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>

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I am sorry, &quot;AEST&quot; was wrong. I can&#39;t work out what timezone code it is, but my default timezone here in eastern australia prints as: &gt; as.POSIXct(&quot;1970-01-01&quot;, tz=&quot;&quot;) [1] &quot;1970-01-01 AUS Eastern Daylight Time&quot;
 and that is the one that has repeated dates before 1970. But I take your point that it is fundamentally a problem with Windows. --Felix <div>On 3/19/07, 
Prof Brian Ripley &lt;<a href="mailto:ripley at stats.ox.ac.uk">ripley at stats.ox.ac.uk</a>&gt; wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hmm, AEST is not a valid time zone on Windows. See ?as.POSIXlt for one of several places where this is documented. But in any case, the underlying problem is in the OS, and we only try to work around it to the best of our knowledge (and that excludes
 undocumented time zones). On Mon, 19 Mar 2007, <a href="mailto:felix at nfrac.org">felix at nfrac.org</a> wrote: &gt; Times from seq.POSIXt come out wrong in AEST timezone around Feb 29 every &gt; leap year before 1970 (on Windows XP).
 &gt; &gt; According to help(DateTimeClasses), this is handled by &quot;our own C code&quot;. &gt; &gt;&gt; x &lt;- as.POSIXct(&quot;1968-02-27&quot;) # tz=&quot;AEST&quot; &gt;&gt; x.gmt &lt;- as.POSIXct(&quot;1968-02-27&quot;, tz=&quot;GMT&quot;)
 &gt;&gt; data.frame( &gt;&nbsp;&nbsp;&nbsp;&nbsp; GMT=seq(x.gmt, by=&quot;day&quot;, length=8), &gt;&nbsp;&nbsp;&nbsp;&nbsp; byday=seq(x, by=&quot;day&quot;, length=8), &gt;&nbsp;&nbsp;&nbsp;&nbsp; byDST=seq(x, by=&quot;DSTday&quot;, length=8)) &gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; GMT&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;byday&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;byDST
 &gt; 1 1968-02-27 1968-02-27 1968-02-27 &gt; 2 1968-02-28 1968-02-28 1968-02-28 &gt; 3 1968-02-29 1968-03-01 1968-03-02 &gt; 4 1968-03-01 1968-03-02 1968-03-02 &gt; 5 1968-03-02 1968-03-02 1968-03-02 &gt; 6 1968-03-03 1968-03-03 1968-03-03
 &gt; 7 1968-03-04 1968-03-04 1968-03-04 &gt; 8 1968-03-05 1968-03-05 1968-03-05 &gt; &gt;&gt; R.version &gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; _ &gt; platform&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; i386-pc-mingw32 &gt; arch&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; i386 &gt; os&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mingw32
 &gt; system&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; i386, mingw32 &gt; status &gt; major&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2 &gt; minor&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.1 &gt; year&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2006 &gt; month&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;12 &gt; day&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;18 &gt; svn rev&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;40228 &gt; language&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; R
 &gt; version.string R version 2.4.1 (2006-12-18) &gt; &gt; &gt; &gt; -- Brian D. Ripley,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="mailto:ripley at stats.ox.ac.uk">ripley at stats.ox.ac.uk</a> Professor of Applied Statistics,&nbsp;&nbsp;
<a href="http://www.stats.ox.ac.uk/~ripley/">http://www.stats.ox.ac.uk/~ripley/</a> University of Oxford,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Tel:&nbsp;&nbsp;+44 1865 272861 (self) 1 South Parks Road,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +44 1865 272866 (PA) Oxford OX1 3TG, UK&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Fax:&nbsp;&nbsp;+44 1865 272595
 </blockquote></div>

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