This can be placed anywhere on your desktop, where it will display the current date.
The preferences let you set U.S.-style and Euro-style dates. You can also make the weeks start on Sunday or Monday. If you don't want the calendar floating on your screen, you can choose the non-floating window option.
You can set the transparency option from nearly invisible to solid. You can also jump to a specific month and year in case you need to see what day something happened in the past. Navigate through years from one to 9999.