The preferences dialog of the gnome clock applet only allows very few options for choosing the date/time format. For instance, it is not possible to show the date without displaying the abbreviated month name as well. Since most users will always know the current month, this information is not actually necessary and only wastes space in the panel. I'd suggest adding an "Advanced" button to the preferences dialog which allows users to specify the date/time format using a strftime-like configuration string. This would give users the possibility to freely choose nearly any format they like without making the dialog too complicated.