Sex Calendar Method. Days 8 through 19 of every cycle are considered fertile days for all users of the standard days method. Calendar method family planning, also known as the rhythm method, is a form of natural family planning.

One form of natural family planning is the calendar method (or the fertility awareness method or the rhythm method). There are a few natural family planning methods that can help inform a woman of her most fertile days, like the billings ovulation method and basal body temperature method.