calendar-scroll-left-three-months is an interactive autoloaded Lisp function in `cal-move.el'.

(calendar-scroll-left-three-months ARG &optional EVENT)

Scroll the displayed calendar window left by 3*ARG months.
If ARG is negative the calendar is scrolled right. Maintains the relative
position of the cursor with respect to the calendar as well as possible.
EVENT is an event like `last-nonmenu-event'.