Tangentially, I frequently add dates to filenames to keep things organized. And _always_ in the `YYYYMMDD` format for clarity and technical reasons; `DDMMYYYY` (or God forbid the Americans' `MMDDYYYY`) never made much sense to me.
(defun mdy ()
(interactive)
(insert (format-time-string "%04Y-%02m-%02d")))
Then to create a date-stamped file name:
(defun file-mdy (file-name)
(interactive "sbasename: ")
(find-file (format "%s-%s.org" (format-time-string "%04Y-%02m-%02d") file-name))
(save-buffer))
Nobody seems to misunderstand this date format. US folks might find it annoying, but understand what it means.