Use
AddSpecialDate method. See documentation for details on this method.
Calendar1.AddSpecialDate(-1, 7, 4, "Independence Day", "specialDateJuly4", "specialDateJuly4Over", "");
Calendar1.AddSpecialDate(-1, 6, 14, "Special Day", "mySpecialDate1", "mySpecialDate1Over", "");
Calendar1.AddSpecialDate(-1, 6, 28, "Another special day", "mySpecialDate2", "mySpecialDate2Over", "");