Always keep your menstrual cycle information up-to-date.
Your Days free ovulation calendar calculates your fertility based on your menstrual cycle information. Therefore, to ensure that the calendar shows your fertility correctly, the menstrual cycle information must be up-to-date.
Your menstrual cycle can have occasional variations in length. Don't worry about these slight variations: about 50 percent of healthy women have cycles that are occasionally irregular, and Your Days free ovulation calendar takes these variations into account. But if you don't update your menstrual cycle information for a long time, these variations accumulate, and this may lead to incorrect fertility predictions.
To keep the calendar accurate, you should update your menstrual cycle information at least once every two months.
Yes, Your Days free ovulation calendar will a show a message, letting you know that you need to update your information.

To update your menstrual cycle information, click the link update days in Options area
See Editing Menstrual Cycle Data information for more details.