NTP - A little information on using NTP on fedora core.

Some ntp servers that I trust are:
time-a.nist.gov
time-b.nist.gov

Another thing to do, is use a pool ntp servers:
pool.ntp.org
This basically is a round robin DNS that distributes your request across multiple servers.
(I usually default to this if all the other trusted servers fail.

Before starting the ntpd daemon, run ntpdate to synchronize your clock with a time server. ntpd will not synchronize your clock with a time server if your system clock is significantly off NTP time.
ntpdate -u <ntp server>

The graphical user interface utility redhat-config-date (Red Hat Linux) or system-config-date (Fedora Core) may also be used to administer ntp.

Here is my typical config:

# Prohibit general access to this service.
#restrict default ignore

# Permit all access over the loopback interface.  This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 127.0.0.1

# -- CLIENT NETWORK -------
# Permit systems on this network to synchronize with this
# time service.  Do not permit those systems to modify the
# configuration of this service.  Also, do not use those
# systems as peers for synchronization.
# restrict 192.168.1.0 mask 255.255.255.0 notrust nomodify notrap

# --- OUR TIMESERVERS -----
server time-a.nist.gov
server time-b.nist.gov
server pool.ntp.org

# --- GENERAL CONFIGURATION ---
# Undisciplined Local Clock. This is a fake driver intended for backup
# and when no outside source of synchronized time is available. The
# default stratum is usually 3, but in this case we elect to use stratum
# 0. Since the server line does not have the prefer keyword, this driver
# is never used for synchronization, unless no other other
# synchronization source is available. In case the local host is
# controlled by some external source, such as an external oscillator or
# another protocol, the prefer keyword would cause the local host to
# disregard all other synchronization sources, unless the kernel
# modifications are in use and declare an unsynchronized condition.
server  127.127.1.0     # local clock
fudge   127.127.1.0 stratum 10

#
# Drift file.  Put this in a directory which the daemon can write to.
# No symbolic links allowed, either, since the daemon updates the file
# by creating a temporary in the same directory and then rename()'ing
# it to the file.
#
driftfile /var/lib/ntp/drift
broadcastdelay  0.008

#
# Authentication delay.  If you use, or plan to use someday, the
# authentication facility you should make the programs in the auth_stuff
# directory and figure out what this number should be on your machine.
#
#authenticate yes
disable auth
statistics sysstats peerstats
enable stats

#
# Keys file.  If you want to diddle your server at run time, make a
# keys file (mode 600 for sure) and define the key number to be
# used for making requests.
#
# PLEASE DO NOT USE THE DEFAULT VALUES HERE. Pick your own, or remote
# systems might be able to reset your clock at will. Note also that
# ntpd is started with a -A flag, disabling authentication, that
# will have to be removed as well.
#
keys            /etc/ntp/keys

Created: 2005-03-26 15:22:28 Modified: 2005-04-28 09:18:20