After you get serious and set up a domain at home, suddenly the option to synch with internet time vanishes from all your computers. They're expecting to synch with the domain controller. Great, but how do you synch the domain controller with a time-server? Like this (at a command prompt, obviously)
net time /setsntp:0.au.pool.ntp.org
net stop w32time
net start w32time
You have to roll the service to make it pick up the change.
This server is for Queensland, Australia. Use Google to find a time-server for your locale.