Generally, your ovulation date occurs about two weeks before the first day of your period. This can be anywhere from day 11 to day 21 of a cycle, but the range can be even wider for those with irregular cycles. Ovia predicts your "fertile window" using the data you log about yourself, making it less of a guessing game. Some women notice slight body changes when they ovulate, including minor cramping, increased sex drive, and light spotting. Read more about the fertile window and predicting ovulation here.