Are microseconds or nanoseconds specified in POSIX, if either of them 
are? I took a quick peek at:

http://www.unix.org/single_unix_specification/

... and its sys/stat.h only includes a single time_t st_mtime, which 
makes it look as though neither microseconds nor nanoseconds are part 
of the standard.

Why did we choese nanoseconds?

Thanks in advance.

-Marc