calendar-make-alist is a compiled Lisp function in `calendar.el'.

(calendar-make-alist SEQUENCE &optional START-INDEX FILTER &rest SEQUENCES)

Return an association list corresponding to SEQUENCE.
Associates each element of SEQUENCE with an incremented integer,
starting from START-INDEX (default 1). Applies the function FILTER,
if provided, to each key in the alist. Repeats the process, with
indices starting from START-INDEX each time, for any remaining
arguments SEQUENCES.