but only with some messing about.
This is taken from macosxhints.com
While not strictly required, having the Developer Tools installed will make it easier.1. Open the Terminal and type:cd /System/Library/CoreServices/Menu Extras/cd Clock.menu/Contents/Resources/English.lproj/[NOTE: Shown on two lines for a narrower article display; you can obviously enter this as one long 'cd' command].2. Then change the permissions on the Localizable.strongs file, perhaps easiest is chown:sudo chown username Localizable.stringsThat is if your short username was 'fred', you'd type: sudo chown fred Localizable.stringsIt should then ask for your password, enter it.3. If you don't have the Dev Tools installed, you'll need to navigate to the Localizable.strings file in the Finder first -- open the application bundle by control-clicking it and selecting "Show Package Contents", then open Contents -> Resources -> English.lproj, revealing the Localizable.strings file. Drag and drop this file onto your text editor of choice (launch it if it's not already running). If you have the Dev Tools, skip this step.4. Now open Localizable.strings with PropertyList Editor (located in Developer/Applications). If you have a good text editor that should work as well, but I had no luck with BBedit, something to do with Unicode I think. Since you 'chowned' the file (or because you're running your editor as root through Pseudo), you'll have the ability to save your changes. One advantage of PropertyList Editor over a standard editor is that you can use the File -> Open menu to navigate into the application bundles and open the bundled files directly.5. Look for the entry for MBC_DATETIME_MENUITEM_FORMAT, which will have a lot of % symbols in its value. The format does obey the standard UNIX date formats. I'm using %A, %d %B %Y which gives me it in the format "Saturday, 17 November 2001", which is my personal preference. Type man strftime in the Terminal for all the choices. You can also include straight text, e.g. "Today is...".You may wish to play around with the settings in a terminal window first to determine what you like. To do that, just type date "+%option %option text whatever", where each %option is replaced by one of the formatting pairs from 'strftime' and text whatever is optionally any raw text you'd like to see. When you hit ENTER, you'll see the date displayed in your described format. My personal choice, since I have the menubar clock already displaying the day of the week, is simply "%b %d, %Y" which results in what you see in the image at the top of this article. Note that you need to include the + sign and the quotes in the Terminal, but you do not include either when editing the file!6. Finally, log out and in again to see your changes.