For some strange reason, none of my Ubuntu 6.10 installations have included NTP (Network Time Protocol) by default. No idea why, but here is how you make sure the clock your Ubuntu box is staying in sync with the rest of the world if the same thing happens to you.
# sudo apt-get install ntp-server
This is technically it, but the stock installation does not adjust your time right away if it is way out of sync. So we just do this to make sure we're correct from the start:
# /etc/init.d/ntp-server stop
# ntpdate -s pool.ntp.org
# /etc/init.d/ntp-server start
There, you're in sync and will stay in sync from now on.