suggested edit to hint: Tip — Date and Time in the Menu Bar
The simpler way is to do:
1. Click >System Preferences...>International>Formats.
2. Next to "Dates", click the "Customize" button.
3. Arrange the date the way you want it to appear in the menu bar (don't worry about time at this point).
4. Select everything in the date format box and copy it (⌘C).
5. Next to "Times", click the "Customize" button.
6. Select the "Medium" format.
7. Paste the time format into the box (⌘V), and customize it to appear as you wish.
8. Click OK.
That's it. No Terminal, nothing complicated.
17" iMac 2GHz Intel Core 2 Duo 2.5GB RAM 160GB hard drive, Mac OS X (10.5.5), iPod 5th gen (with video) 30GB.