[R] Date, date, POSIX question

[Joe W. Byers]

I have been working with R extensively for several months.  I switched 
from SAS and Matlab to R.  My question is

Can anyone explain the benefits and detractions of the 'Date' package 
verses the 'date' package and verses 'POSIX' dates.

I have noticed several other packages use one or the other.  Rmetrics 
seems to standardize on POSIX.  I can only see differences in default 
formats, and the starting counting number be it 1 1 1900 or something else.

I am trying to standardize code that I write for research and to provide 
to my students on one date schema.  The documentation is very good on 
using a specific package, but I can not tell the which one provides the 
broadest coverage across R packages or is just the better one to use.

I know all of you have more experience with some of these and I am just 
soliciting your opinions and comments.

Thank you
Joe