NTP

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

ntpdate -q

chkconfig --list | grep ntpd

If all the columns are 'off', then it's not enabled.

You can use the following command to enable NTP:

yum install ntpd
chkconfig ntpd on

Then use the following command to start it:

service ntpd start

You can check if the time is in sync using:

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 arricade.rack9.