I was surfing around and finally found out how to add the date to the OSX menu bar without installing additional software!
The tip says you need to use the medium category, but only the Long category for Times worked for me. This may be due to a difference between 10.5 and 10.4.
The following tip
Want to see the date in the menubar? Start by opening the International Preferences panel, and clicking the Formats tab.
In the Dates section, click Customize. Click the Show pop-up and select your choice of Short, Medium, etc. Now place the elements you want in the small “work area,” by dragging and dropping them from the Date Elements section. Once placed, you can click on some elements to see other options (Wednesday or Wed, for instance). Once you’ve built the date string you want, click once in the work area, and hit Command-A then Command-C to select the string and copy it. Now click Cancel to close the window without making any changes.
In the Times section, click Customize, and set the Show pop-up to Medium. In the small work area below the pop-up, place the curser where you want the date elements to start, and click to position the cursor. Now hit Command-V to paste the elements you just copied. You can further add characters and spaces to customize the look. If you want to remove an element (i.e. the year), click on it and use the Delete key. Click OK, and you’ll see the results in the menubar.
MacOSXHints
Since a picture is worth a thousand words here is how I have Time Long set
ErikPersson.com 