Fertility calendars help to pinpoint your fertile days and, in turn, help increase your chances of conceiving. Every woman, and every woman's menstrual cycle, is different. If you are trying to conceive, you can increase your chances of getting pregnant by having sex during the most fertile times of your cycle. There are several ways to chart your fertility cycle, including body temperature, cervical mucus, or purchasing an ovulation predictor kit. One of the first, easiest, and least expensive options try is the calendar method. We personally do not promote fertility calendars as a reliable or effective way to prevent pregnancy.
There are a variety of web-based calendars available on the internet, with all the information you need, and more. There really is no need to 'buy' a specialty fertility calendar, as the information is readily available with a quick search for 'fertility calendar'. Grab a pocket book or wall calendar to chart all the information and you'll learn pretty quickly what to look for (and when to look for it) if you're trying to conceive.