The fertile days of the female menstrual cycle are determined using the symptothermal method with the help of the Ovy App. This involves evaluating changes in basal temperature and cervical mucus or the cervix. With the Ovy Bluetooth Basalthermometer, which automatically transfers the basal temperature to the Ovy App after morning measurement without needing to open the app. With the Ovy Basal Thermometer, which requires manual entry of the temperature into the Ovy App in the morning. With a conventional basal thermometer that measures to two decimal places.