How do I add a specific time-server?

At work I can only connect to a specific ntp time-server. Under Ubuntu 10.10 I was able to add that server somewhere under time/date settings. Now under Ubuntu 11.04 I cannot find that option anymore.

I am sure that there is a config somewhere that I can edit to add the approved server.

Can you please give me some pointers?

Edit: I should probably mention that I use the classic desktop.

You'll have to do some manual editing using nano, or your editor of choice:

sudo nano /etc/default/ntpdate

and change the NTPSERVERS="ntp.[your-server-here]"

If you restart your computer this change will be made active. If you're feeling impatient and don't want to wait for the server to automatically update you can do it manually:

sudo ntpdate-debian

I can't see a GUI option for this, but I could be wrong.