The Vita Nuova man pages are woefully outdated. You might want to consider purchasing the printed 9front man pages.
http://9front.org/propaganda/books
Of course the most up-to-date man pages are available via man after a sysupdate.
For what I need, in fact I can simply use nsec(2), diffing nanoseconds
times! (I have the printed manuals from Vita Nuova, I should remember
to read the man pages first in printed form at leisure...)