The other thing you have to worry about, Wolfgang, is the accuracy of 
that "monotonically increasing counter" - is it in fact ticking at 
the frequency that matches what it claims to be?

This is the other problem that NTP is designed to deal with, in 
addition to keeping the correct time of day. If you're running a 
properly configured ntpd now, go look at /var/run/ntp.drift or run

	ntpdc -c loopi

and look at the frequency - that's a correction for the local system 
clock that ntpd is applying by slewing the clock. The closer it is to 
zero, the better off you are, but the variance (even in nominally 
identical systems!) is larger than you might think.

	Erik <fair@clock.org>