NTP

You can use the following command to check if it's enabled:

 pgrep ntpd

You can use the following command to enable NTP:

yum install ntpd
chkconfig ntpd on
service ntpd start

Make sure your nameserver (DNS) is configured  correctly (see Modify the dhcp client configuration).

You can change the servers to synchronize NTP in /etc/ntp.conf

You can change your local timezone with the /etc/localtime link

To synchronize NTP:

ntpq -p

It will display a list of servers and the server which is currently synced should be prepended by a '*'. For example:

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*barricade.rack9 209.51.161.238   2 u 1001 1024  377   31.147   -0.369  20.074
+ip-72-167-42-82 204.123.2.5      2 u  754 1024  377  166.388  -29.692  28.223
+cheezum.mattnor 129.7.1.66       2 u   91 1024  377   45.715    1.504  47.753

In this case the host's time is synced with barricade.rack9.