display-time
display-time is an interactive autoloaded Lisp function in `time.el
'.
(display-time)
Enable display of time, load level, and mail flag in mode lines.
This display updates automatically every minute.
If `display-time-day-and-date' is non-nil, the current day and date
are displayed as well.
This runs the normal hook `display-time-hook' after each update.