How do I use pool.ntp.org?
If you just want to synchronise your computers clock to the network, the configuration file (for the ntpd program from the ntp.org distribution, on any supported operating system - Linux, *BSD, Windows and even some more exotic systems) is really simple:
driftfile /var/lib/ntp/ntp.drift
server 0.pool.ntp.org
server 1.pool.ntp.org
server 2.pool.ntp.org
server 3.pool.ntp.org
The 0, 1 and 2.pool.ntp.org names point to a random set of servers that will change every hour. Make sure your computer's clock is set to something sensible (within a few minutes of the 'true' time) - you could use ntpdate pool.ntp.org, or you could just use the date command and set it to your wristwatch. Start ntpd, and after some time (this could take as long as half an hour!), ntpq -pn should output something like:
avbidder:~$ ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
+81.6.42.224 193.5.216.14 2 u 68 1024 377 158.995 51.220 50.287
*217.162.232.173 130.149.17.8 2 u 191 1024 176 79.245 3.589 27.454
-129.132.57.95 131.188.3.222 3 u 766 1024 377 22.302 -2.928 0.508
The IP addresses will be different, because you've been assigned random timeservers. The essential thing is that one of the lines starts with an asterisk (*), this means your computer gets the time from the internet - you'll never have to worry about it again!
As pool.ntp.org will assign you timeservers from all over the world, time quality will not be ideal. You get a bit better result if you use the continental zones (For example europe, north-america, oceania or asia.pool.ntp.org), and even better time if you use the country zone (like ch.pool.ntp.org in Switzerland) - for all these zones, you can again use the 0, 1 or 2 prefixes, like 0.ch.pool.ntp.org. Note, however, that the country zone might not exist for your country, or might contain only one or two timeservers. If you know timeservers that are really close to you (measured by network distance, with traceroute or ping), time probably will be even better.
If you're using a recent Windows version, you can also use the ntp client that is built into the system. Just execute:
net time /setsntp:pool.ntp.org
With some versions of Windows you can also specify more than one server
net time /setsntp:"0.pool.ntp.org 1.pool.ntp.org 2.pool.ntp.org"
at the command prompt. This is known to work on Windows 2000/XP/2003. The same can be achieved by, as administrator, right-clicking the clock in the taskbar, selecting 'Adjust Date/Time' and entering the server name in the 'Internet Time' tab.
Meinberg made a port of the ntp daemon for windows.
If your Windows system is part of a domain, you might not be able to independently update your computer time. See How Windows Time Service Works.
Additional Notes
If you have a static IP address and a reasonable Internet connection (bandwidth is not so important, but it should be stable and not too highly loaded), please consider donating your server to the server pool. It doesn't cost you more than a few hundred bytes per second traffic, but you help this project survive. Please read the joining page for more information.
If your Internet provider has a timeserver, or if you know of a good timeserver near you, you should use that and not this list - you'll probably get better time and you'll use fewer network resources. If you know only one timeserver near you, you can of course use that and two from pool.ntp.org or so.
It can rarely happen that you are assigned the same timeserver twice - just restarting the ntp server usually solves this problem. If you use a country zone, please note that it may be because there is only one server known in the project - better use a continental zone in that case. You can browse the zones to see how many servers we have in each zone.
Be friendly. Many servers are provided by volunteers, and almost all time servers are really file or mail or webservers which just happen to also run ntp. So don't use more than three time servers in your configuration, and don't play dirty tricks with burst or minpoll - all you will gain is that this project will be stopped sooner or later.
Make sure that the time zone configuration of your computer is correct. ntpd itself does not do anything about the time zones, it just uses UTC internally.
If you are synchronising a network to pool.ntp.org, please set up one of your computers as a time server and synchronize the other computers to that one. (you'll have some reading to do - it's not difficult though. And there's always the comp.protocols.time.ntp newsgroup.)
At this point, I'd like to thank those donating their time and timeservers to this network.