Fertility Plus offers a downloadable chart for keeping track of your basal body temperature (taken each morning before getting out of bed), which rises during the luteal phase because of increased levels of progesterone.
Instead of this being a discouraging discovery, use the knowledge to work with your doctor to balance your progesterone, which regulates the luteal phase, in order to increase your chances of getting pregnant.
The length of this time period is extremely important in getting pregnant; women whose luteal phase is between 12-16 days get pregnant much more easily than women whose luteal phase is only 10 or 11 days.
The ovulation calculator itself require three pieces of information: the date of your last period, the length of your menstrual cycle, and the length of your luteal phase.
The time in between ovulation and when your next period starts is called the luteal phase.