strptime format = "%H:%M:%OS6"

I read a dataset with times in them, e.g., "09:31:29.18761".
I then parse them:

all$X.Time <- strptime(all$X.Time, format = "%H:%M:%OS6");

and get a vector of NAs (how do I check that except for a visual  
inspection?)
then I do

options("digits.secs"=6);
all$X.Time <- strptime(all$X.Time, format = "%H:%M:%OS");

and it, apparently, works:

all$X.Time[2]-all$X.Time[1]

Time difference of 5.12188 secs
so, why doesn't format = "%H:%M:%OS6" work as documented?

I don't know. I get similar results on a Mac (not the most recent  
version of R obviously). I interpreted the section to mean that the  
format string was just "%OS<n>" but tried it both ways with identical  
non-results.

 > x <- "09:31:29.18761"
 >
 > y <- strptime(x, format = "%OS");
 > y
[1] "2011-02-15 00:00:09"
 > x <- "09:31:29.18761"
 >
 > y <- strptime(x, format = "%OS6");
 > y
[1] NA
 > y <- strptime(x, format = "%H:%M:%OS3");
 > y
[1] NA

Also got NAs with %OS1 through %OS5


 >  sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)

locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods
[7] base

other attached packages:
[1] sos_1.3-0       brew_1.0-4      lattice_0.19-13

loaded via a namespace (and not attached):
[1] grid_2.12.1  tools_2.12.1

-- 
Sam Steingold (http://sds.podval.org/) on CentOS release 5.3 (Final)

David Winsemius, MD
West Hartford, CT