(defun periodise ()
  (setq periodfile "~/Documents/drive/org/period.org")
  (find-file-noselect periodfile)
  (setq thebuffer (file-name-nondirectory periodfile))
  (with-current-buffer thebuffer
    (setq theyear (string-to-number (buffer-substring-no-properties 2 6)))
    (setq themonth (string-to-number (buffer-substring-no-properties 7 9)))
    (setq thedate (string-to-number (buffer-substring-no-properties 10 12)))
    (kill-buffer thebuffer))
  (setq dayof nil)
  (push theyear dayof)
  (push thedate dayof)
  (push themonth dayof)
  (setq thatday (calendar-absolute-from-gregorian dayof))
  (setq today (calendar-absolute-from-gregorian (calendar-current-date)))
  (setq days (+ 1 (- today thatday)))
  (insert (concat "Day " (format "%S" days))))

(defun menstruate ()
  (interactive)
  (setq periodfile "~/Documents/drive/org/period.org")
  (find-file-noselect periodfile)
  (setq thebuffer (file-name-nondirectory periodfile))
  (with-current-buffer thebuffer
    (goto-char (point-min))
    (insert "\n")
    (goto-char (point-min))
    (org-time-stamp '(16) nil)
    (write-file periodfile)
    (kill-buffer thebuffer)))