This tip from Lifehacker today works fine except step 5 needs to read:
"Paste the date format on your clipboard to the left of the time format, insert a space to the right of the day, and hit OK."

Otherwise, there is no space between the numeral(s) for the day and the numeral(s) for the hour.

This is great. I have wanted this for a long time. Here is the link:
http://lifehacker.com/software/mac-tip/display-the-date...e-menubar-316029.php

I often use the Julinan Day of the year for dating the projects for one of my customers.
Before I would go to the Termainal.app and type "Cal -jy 2008" to look it up. Now I can have it in my menu bar.

This worked except for step 4.
I had to alter the Time Long format.

4. Hit the Customize button next to Times. Choose the "Long" format.

I'm using OS X 10.4.11 on a PowerBook G4.

I had no idea this could be done in System Preferences.
Thanks!

Well, after changing a bunch of things I reset my international settings to US.
Then, I had to alter the Time Medium format.
Go figure, your milage may vary.

Here's one I used to change my formatting...
MacInstruct: How to Display the Date in the Menu Bar
I think one of our members made it known quite some time ago.