I have a few Ubuntu servers scattered across the earth. This is all I had to do to make sure that their system clocks were synchronized:
sudo apt-get install ntp ntpdate
Those Ubuntu packages are automatically configured to make your box use the time server at ntp.ubuntu.com. It couldn’t be any simpler.
By the way, if you want to point to a different time server, the config file in /etc/ntp.conf is full of helpful comments.