strptime and "impossible" dates

Typically, when I use strptime with "impossible" dates I get an NA, which is
what I expect.

version

_                   
platform sparc-sun-solaris2.6
arch     sparc               
os       solaris2.6          
system   sparc, solaris2.6   
status                       
major    1                   
minor    3.0                 
year     2001                
month    06                  
day      22                  
language R

strptime("20001132", format = "%Y%m%d")

[1] "NA"

But this is not always the case, consider the impossible case of November 31, 2000

strptime("20001131", format = "%Y%m%d")

[1] "2000-12-01"

Shouldn't the answer here be NA? I would submit this as a bug except that I
suspect that the problem is my misunderstanding of the role of seconds and time
zones is this function . . .

Thanks for any pointers. I have read the help pages and the excellent
discussion in the recent R Newsletter.

Dave Kane
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._