Where does ntpdate get its settings from and what is the "no servers can be used" error about?

After mucking around for most of the day, I have come to the following conclusion:

ntpdate-debian is the version to use if you want to use a config script, and in that case, you would edit the /etc/default/ntpdate file.

ntpdate cannot be used without arguments nor does it have a config file. If you want to use this to update, you have to state the ntp server in an argument, such as ntpdate ntp.ubuntu.com.