javascript calcate between days

gistfile1.js

function betweenDays(first_date, second_date, separator) {
	var separator = separator || "-",
		first_date_parts = first_date.split(separator),
		second_date_parts = second_date.split(separator),
		first_date_object = new Date(first_date_parts[0], first_date_parts[1], first_date_parts[2]),
		second_date_object = new Date(second_date_parts[0], second_date_parts[1], second_date_parts[2]),
		between_time = Math.abs(first_date_object.getTime() - second_date_object.getTime());
	
	return between_time/(1000*60*60*24);
}

betweenDays("2011/06/01", "2011/06/02", "/");
betweenDays("2011-06-01", "2011-06-02");