Here is basic overview of setting up NTP by GUI and also by terminal command. You have to be logged in as root user.
1.) Click on System -> Admin -> Date & Time
2.) Make sure Synchronize is checked. Then add and delete the servers you want. Then Click ok to exit.
3.) To Verify : Open a terminal as root or "su"
It any entry is starred, it means Venice is synced to that server. The entries '+' , means the server is in standby for sync if the currently synced one goes down. If none is starred, wait 5 mins and try again.
Configure NTP by Command Only : -
1.) Open a Terminal and run these commands as root or 'su'.
a.) service ntpd stop <--- Stop NTP service
b.) gedit /etc/ntp.conf & <---here any entries with 'server' at the beginning you want to comment out and add your own server.
For Example in - 'server 0.rhel.pool.ntp.org '. Replace with 'server my_new_ntp_server.com' Then save file and quit.
If your time server is locally hosted (like 192.168.X.X ), check with your IT admin and add exceptions as noted in comments in the ntp.conf file. The default port is 123. If you port is non default , you may have to add that as an exception using command 'iptables'.
c.) service ntpd start <---Start ntp service
d.) chkconfig ntpd on <---Will ensure ntp starts at boot up.
2.) Perform step 3 above to Verify.