re: Nagios timezone setting, see this thread:
http://www.mail-archive.com/nagios-u.../msg09072.html
re: nfsen -- it has not been added to the ports tree, so you are on your own with it. The nfdump component was ported, in early 2008, but was not added to the tree due to lack of testing. If you are interested, you can obtain it here:
http://marc.info/?l=openbsd-ports&m=120554061827759&w=2