The gateway and DNS will be needed for NTP server. And with the Continuous adjusting, using the NTP option enabled on your system, time will be monitored and corrected if the difference between the local time and the server time changes. Enabling this option is especially recommended when using domains.

So please make sure you have appropriate gateway and DNS settings.

The gateway and (with host names) DNS network settings must be configured before the NTP.

Also please make sure that you have Internet access and proper network setup, especially the gateway and DNS. You can check proper Internet access by using ping from the console tools. At the console, press Ctl-Alt-T. Select 'Ping'.
To use this option you must set the correct NTP server in the Time zone settings function.