[R] Chron, as.POSIXct problem

[Philippe Glaziou]

Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
> Does not happen on Solaris or Linux, so looks like a MacOS X problem.

It does not happen on my Mac G4 box (R 1.8.0 on MacOSX 10.2.6). 

--Philippe




> Here is some crosschecks:
> 
> > unclass(datesTest)
> [1] -6301 -6300 -6299
> attr(,"format")
> [1] "m/d/y"
> attr(,"origin")
> month   day  year
>     1     1  1970
> > unclass(as.POSIXct(datesTest))
> [1] -544406400 -544320000 -544233600
> 
> 
> On Wed, 12 Nov 2003, Brian Beckage wrote:
> 
> > Dear R list,
> > 
> > I noticed the following 'problem' when changing the format of dates 
> > created with seq.dates() (from the Chron library) using as.POSIXct() 
> > (R 1.8.0 on OSX 10.2.8):
> > 
> > >  datesTest<-seq.dates(from="10/01/1952", length=3, by="days");
> > >  datesTest
> > [1] 10/01/52 10/02/52 10/03/52
> > 
> > # Now changing the format to show year as 1952.
> > 
> > >  datesTest<-format(as.POSIXct(datesTest), "%m/%d/%Y")
> > >  datesTest
> > [1] "09/30/1952" "10/01/1952" "10/02/1952"
> > >
> > 
> > The dates were shifted by one day.  The work around is simple enough, e.g.,
> > 
> > >  datesTest<-format(as.POSIXct(datesTest+1), "%m/%d/%Y")
> > [1] "10/01/1952" "10/02/1952" "10/03/1952"
> > 
> > but I wonder if this is the intended behavior?
> > 
> > Brian
> > 
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> > 
> > 
> 
> -- 
> 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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-- 
Philippe