[R] documenting quirky behavior of as.POSIXct, as.POSIX.lt regarding AM/PM, possibly other cases

[David Winsemius]

Also works as expected on the MacOSX 64 bit binary for R 2.8.1  
(patched).

On May 5, 2009, at 4:06 PM, jim holtman wrote:

> 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 at 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?
>>
> -- 
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
>
> What is the problem that you are trying to solve?

David Winsemius, MD
Heritage Laboratories
West Hartford, CT