ntpdate sets the local date and time by polling the Network Time Protocol (NTP) server(s) given as the server
arguments to determine the correct time.

To setup ntpdate statup once under Debian or Ubuntu Linux use any one of the following command:
Text based GUI tool, type the command and selecct ntpdate
Use command line tool update-rc.d:
update-rc.d ntpdate defaults
Ubuntu lovers err users type
sudo update-rc.d ntpdate defaults
For information can be obtained by typing following command
man rcconf
man update-rc.d

Read FAQ Ubuntu Linux how to set the date and time via Network Time Protocol (NTP)