1) make sure the DNS works

sudo vi /etc/resolv.conf
cat /etc/resolv.conf

nameserver 208.67.222.222
nameserver 208.67.220.220
nameserver 192.168.16.1

2) check that you have ntpd installed

cat /etc/ntp.conf

3) make it work in all

/sbin/chkconfig --list | grep ntpd
sudo /sbin/chkconfig --level 2345 ntpd on

4) Initial sync

sudo /usr/sbin/ntpdate pool.ntp.org

5) Start service / restart

sudo /sbin/service ntpd start