It is normal for menstruation to occur 17 days after ovulation. Normally, menstruation occurs about 14 days after ovulation. After ovulation, the basal body temperature rises due to the formation of the corpus luteum, which usually lasts about 12 days. When the corpus luteum gradually atrophies, the basal body temperature tends to fall, and menstruation will occur within 12 hours after the basal body temperature falls. If the time of luteal atrophy is pushed back after ovulation, the time of the next menstruation will also be pushed back. Therefore, it takes 17 days after ovulation for menstruation to occur because the time of luteal atrophy is prolonged and the time of menstruation will be postponed.