Oh, come on pokey, it is a bit more complex then that!
HOWTO for most Linux distributions (Revised)
There are two ways to go about setting up ntp to sync your clock to atomic clock time. The first and foremost, though, is manually, as pokey has explained.
And to sync the clock by hand, login as root, type the following at a shell:
$ ntpdate time-a.nist.gov
$ hwclock --systohc
Now these commands are all well and good to sync your computer's clock after it's been off for 5 months or so and it's clock is pretty dead, but the other operating systems do not force you to have to set your clock time manually, and neither should you have to. For mission critical time calculations, such as for calculating sattelite uplink speed, you must have both the times set to Atomic clock time. The Sattelite, will, of course use GPS time stamping, and the ground, will run xntpd.
This is a daemon controller that can be set under chkconfig, by running the following as root:
$ chkconfig --add xntpd
Finally, add the ntp servers of your choice from the list panamaus lists above to
Here's an example from my machine: