NRC has published Java clocks for those who want to be sure they have, precisely, the right time! Naturally, you can also use their Network Time Protocol (NTP) server and type:
netdate time.chu.nrc.ca
as root. (This is for Linux machines.)
Windows XP has a builtin NTP client. Go in the control panel, under date/time then “Internet time”.
That is interesting. Once I was thinking how to know the network delay when we want to measure the QoS of Web services. It seems NTP/SNTP can get the difference between your computer time and the server time and the around trip network time. Then you can know preciusly the time.