Produce a daily/weekly view from all files in variable `org-agenda-files'.
The view will be for the current day or week, but from the overview buffer
you will be able to go to other days/weeks.
With a numeric prefix argument in an interactive call, the agenda will
span ARG days. Lisp programs should instead specify SPAN to change
the number of days. SPAN defaults to `org-agenda-span'.
START-DAY defaults to TODAY, or to the most recent match for the weekday
given in `org-agenda-start-on-weekday'. (fn &optional ARG START-DAY SPAN)