.emacs

(defvar current-date-time-format "%a %b %d %H:%M:%S %Z %Y"
  "Format of date to insert with `insert-current-date-time' func
See help of `format-time-string' for possible replacements")

(defvar current-time-format "%a %H:%M:%S"
  "Format of date to insert with `insert-current-time' func.
Note the weekly scope of the command's precision.")

(defun insert-current-date-time ()
  "insert the current date and time into current buffer.
Uses `current-date-time-format' for the formatting the date/time."
       (interactive)
       ;; (insert "==========\n")
       ;; (insert (let () (comment-start)))
       (insert (format-time-string current-date-time-format (current-time)))
       (insert "\n"))

(defun insert-current-time ()
  "insert the current time (1-week scope) into the current buffer."
       (interactive)
       (insert (format-time-string current-time-format (current-time)))
       (insert "\n"))

(global-set-key (kbd "<f5>") 'insert-current-date-time)