You may get a dialog box informing you that NTP support has to be installed. Click on Install NTP Support . The necesary files will be downloaded from the repository.
Once the download is complete Close the Time and Date pop up window. Run it once again from System->Administration-> Time and Date . You will get the following window.
Click on Select servers.
Put a tick mark on the selected server and close the window. The NTP client will start running depending on the configuration file /etc/ntp.conf. You can tweak this file for various time update options.