Insert this line at the end of /etc/rc.d/rc.local:
rdate -s time.ucla.edu
You can use any Network Time Protocol (NTP) server. For a full list, try http://www.eecis.udel.edu/~mills/ntp/servers.htm. Or search Google for “ntp servers”.
You can also run rdate -s time.ucla.edu at the command line anytime to set the system time. Note that you have to run the command as root.