Syncronize system time on RedHat linux

Verify Network Time Protocol is installed and working:

$ pgrep  ntpd

To sync with the time server: 

as ROOT

$ /etc/init.d/ntpd stop

$ /etc/init.d/ntpd start 

OR

$ /etc/init.d/ntpd restart

System - Date and Time - Network time should contain your time server.