I can confirm the issue as well. Only ntp servers from the default list are added to /etc/ntp.conf when checked in the GUI. Custom time servers added via the GUI disappear - they don't get added to ntp.conf, and they don't appear in the custom server list if you close and re-enter the date/time applet.
-- [time-admin] adding ntp server ip from clock applet fails https://launchpad.net/bugs/84194 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
