An information processing device determines a short term length and a long term length so that a timing(s) at which a short-term moving average of a plurality of days of body temperatures measured during past menstrual cycles falls below a long-term moving average of the body temperatures coincides with a menstrual date. The information processing device identifies the timing at which a short-term moving average calculated with the determined short term length exceeds a long-term moving average calculated with the determined long term length, of body temperatures measured during a target menstrual cycle. Based on the identified timing, the information processing device predicts the next menstrual date or estimates the arrival of an ovulation date.
