[R] Does POSIXlt extract date components properly?

[Prof Brian Ripley]

On Tue, 1 Mar 2011, Seth W Bigelow wrote:

> I would like to use POSIX classes to store dates and extract components of
> dates. Following the example in Spector ("Data Manipulation in R"), I
> create a date
>
>> mydate = as. POSIXlt('2005-4-19 7:01:00')
>
> I then successfully extract the day with the command
>
>> mydate$day
> [1] 19
>
> But when I try to extract the month
>
> > mydate$mon
> [1] 3
>
> it returns the wrong month. And mydate$year is off by about 2,000 years.
> Am I doing something wrong?

Not reading the documentation (nor the posting guide). 
?DateTimeClasses says

      ‘mon’ 0-11: months after the first of the year.

      ‘year’ years since 1900.

That is the POSIX standard ... you could also have looked there.

> Dr. Seth  W. Bigelow
> Biologist, USDA-FS Pacific Southwest Research Station
> 1731 Research Park Drive, Davis California
> sbigelow at fs.fed.us /  ph. 530 759 1718
> 	[[alternative HTML version deleted]]

Please note what the posting guide said about that!

> ______________________________________________
> 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