First, what is fertility or menstrual calendar? Fertility or menstrual calendar is a calendar where a woman notes when where her menstrual bleedings. It is called calendar for a reason: fertility calendar has 12 months and each month has up to 31 blank spaces where woman can record any kind of signs that are in gynecological connection. Personally, I am using it for about 7 years now, and I whenever I visit my doctor I show him my calendar. This way he can check very quickly the dates and frequency of my periods.
I think menstrual or fertility calendars are really important because of tracking menstrual cycles, and this way ovulation and period of time cycle forecasts are based totally on the very last acknowledged period date as well as the woman's cycle period. If a woman tracks her cycles and ovulation in this manner, she must understand that this type of tracking is still approximate, because the changes in basal body temperature, cervix position and mucus is still an important part of ovulation calendar and ovulation tracking much more important than calculating the approximate ovulation date. One of the reasons to use fertility (menstrual) calendar is to help you achieve pregnancy, and on the other hand, to help you avoid pregnancy: all you have to do is to record the days of menstrual bleeding. It is also advisable to measure your basal temperature after ovulation date (when the temperature rises) in order to know the length of your luteal phase. The length of luteal phase will help you to calculate the more exact ovulation date.