[R] strptime and "impossible" dates
Prof Brian Ripley
ripley at stats.ox.ac.uk
Tue Jul 24 23:26:33 CEST 2001
On Tue, 24 Jul 2001, David Kane <David Kane wrote:
> Typically, when I use strptime with "impossible" dates I get an NA, which is
> what I expect.
> > version
> platform sparc-sun-solaris2.6
> arch sparc
> os solaris2.6
> system sparc, solaris2.6
> major 1
> minor 3.0
> year 2001
> month 06
> day 22
> language R
> > strptime("20001132", format = "%Y%m%d")
>  "NA"
> But this is not always the case, consider the impossible case of November 31, 2000
> > strptime("20001131", format = "%Y%m%d")
>  "2000-12-01"
> Shouldn't the answer here be NA? I would submit this as a bug except that I
> suspect that the problem is my misunderstanding of the role of seconds and time
> zones is this function . . .
> Thanks for any pointers. I have read the help pages and the excellent
> discussion in the recent R Newsletter.
It depends on the system's strptime. But it would be usual for
out-of-range dates to get normalized as you saw. In general `invalid'
local times (POSIXlt structures) are fixed if they are not seriously
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 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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