とりあえず、これでどう?
ファイル名のとこは適当にいじってくれ。

(add-hook 'after-save-hook
(function (lambda ()
(let ((file-name (buffer-file-name)))
(with-temp-buffer
(insert (concat (time-stamp-dd/mm/yyyy)
" "
(time-stamp-hh:mm:ss)
" "
file-name
"\n"))
(append-to-file (point-min) (point-max)
"~/.file_log"))))))