R help - May 2009 - documenting quirky behavior of as.POSIXct, as.POSIX.lt regarding AM/PM, possibly other cases

I wanted to put this on the R Wiki, but found the suitable pages were read-only.
I wanted to get it out in public to save people work.

I was converting dates like "2009/03/26 01:00:00 AM" using as.POSIXct.
I found that using a format of "%Y/%m/%d %I:%M:%S %p" did not work
correctly to distinguish AM from PM.  Both were converted into the same
timestamp.  Indeed, what I found worked was affixing a space after the string
timestamp to produce "2009/03/26 01:00:00 AM " or "2009/03/26
01:00:00 PM ".  That works.

Didn't see this documented in the associated pages anywhere. 

I wonder if the help system might benefit from user comments like for instance
PHP has?

Seems to work fine for me on R 2.9.0:
> as.POSIXct("2009/03/26 01:00:00 AM" , format="%Y/%m/%d
%I:%M:%S %p" )
[1] "2009-03-26 01:00:00 GMT"
> as.POSIXct("2009/03/26 01:00:00 PM" , format="%Y/%m/%d
%I:%M:%S %p" )
[1] "2009-03-26 13:00:00 GMT"
>

On Tue, May 5, 2009 at 2:55 PM, Galkowski, Jan <jgalkows@akamai.com>
wrote:
>
> I wanted to put this on the R Wiki, but found the suitable pages were
> read-only.  I wanted to get it out in public to save people work.
>
> I was converting dates like "2009/03/26 01:00:00 AM" using
as.POSIXct.  I
> found that using a format of "%Y/%m/%d %I:%M:%S %p" did not work
correctly
> to distinguish AM from PM.  Both were converted into the same timestamp.
>  Indeed, what I found worked was affixing a space after the string
timestamp
> to produce "2009/03/26 01:00:00 AM " or "2009/03/26 01:00:00
PM ".  That
> works.
>
> Didn't see this documented in the associated pages anywhere.
>
> I wonder if the help system might benefit from user comments like for
> instance PHP has?
>
> ______________________________________________
> R-help@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<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

	[[alternative HTML version deleted]]