[R] Problems with as.POSIXct

[Prof Brian Ripley]

What timezone is this?

In America/Bogota there was no midnight that day, so the time would be 
invalid.  The Olson database has

# Colombia
# Rule  NAME    FROM    TO      TYPE    IN      ON      AT      SAVE    LETTER/S
Rule    CO      1992    only    -       May      3      0:00    1:00    S
Rule    CO      1993    only    -       Apr      4      0:00    0 
-
# Zone  NAME            GMTOFF  RULES   FORMAT  [UNTIL]
Zone    America/Bogota  -4:56:20 -      LMT     1884 Mar 13
                         -4:56:20 -      BMT     1914 Nov 23 # Bogota Mean Time
                         -5:00   CO      CO%sT   # Colombia Time

When all else fails, read the help:

      Character input is first converted to class ‘"POSIXlt"’ by
      ‘strptime’: numeric input is first converted to ‘"POSIXct"’.  Any
      conversion that needs to go between the two date-time classes
      requires a timezone: conversion from ‘"POSIXlt"’ to ‘"POSIXct"’
      will validate times in the selected timezone.  One issue is what
      happens at transitions to and from DST, for example in the UK

      as.POSIXct(strptime('2011-03-27 01:30:00', '%Y-%m-%d %H:%M:%S'))
      as.POSIXct(strptime('2010-10-31 01:30:00', '%Y-%m-%d %H:%M:%S'))

      are respectively invalid (the clocks went forward at 1:00 GMT to
      2:00 BST) and ambiguous (the clocks went back at 2:00 BST to 1:00
      GMT).


On Thu, 22 Sep 2011, KENNETH R CABRERA wrote:

> Hi R users:
>
> This is a very strange problem:
>
> Why this instruction shows me NA?,
> and any other date shows me that error!
>
> as.POSIXct(strptime("1992-5-3",format="%Y-%m-%d"))
>
> This is my R version on windows 7.
> "R version 2.13.1 Patched (2011-08-25 r56794)"
>
> Thank you for your help.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
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