(let ((co-date-mark "${co-date}")
      (co-time-mark "${co-time}")
      )
  (goto-char (point-min))
  (while (re-search-forward co-date-mark nil t) (replace-match (getenv "co-date") nil nil))
  (goto-char (point-min))
  (while (re-search-forward co-time-mark nil t) (replace-match (getenv "co-time") nil nil))
  (save-buffer)
  )