tut11.erl

-module(tut11).
-export([month_length/2]).

month_length(Year, Month) ->
	%% All years divisible by 400 are leap.
	%% Years divisible by 100 are not leap. (Except for the 400 rule above)
	%% Years divisible by 4 are leap. (Except for the 100 rule above)
	Leap = if
		trunc(Year / 400) * 400 == Year ->
			leap;
		trunc(Year / 100) * 100 == Year ->
			not_leap;
		trunc(Year / 4) * 4 == Year ->
			leap;
		true ->
			not_leap
		end,
		case Month of
			sep -> 30;
			apr -> 30;
			jun -> 30;
			nov -> 30;
			feb when Leap == leap -> 29;
			feb -> 28;
			jan -> 31;
			mar -> 31;
			may -> 31;
			july -> 31;
			aug -> 31;
			oct -> 31;
			dec -> 31
		end.