Setup NTPD on CentOS

 yum install ntp ntpdate ntp-doc

Turn on service

chkconfig ntpd on

Synchronize the system clock with 0.pool.ntp.org server

ntpdate pool.ntp.org

Start the NTP server

service ntpd start

Configure ntpd (optional)
Edit /etc/ntp.conf

vi /etc/ntp.conf

Set public servers from the pool.ntp.org project:

server 0.rhel.pool.ntp.org
server 1.rhel.pool.ntp.org
server 2.rhel.pool.ntp.org

Restart the NTP server

service ntpd restart