Ovulation usually occurs on the day of ovulation, i.e. within 24 hours. During a normal menstrual cycle, follicles take about 2 weeks to develop and mature. When the hormone levels in the body reach a certain peak, ovulation occurs in the ovaries, so ovulation is only an action that occurs within a time period and does not take up to a day or several days. Although the length of the follicular development period is not fixed, the ovulation period is relatively stable. If the menstrual cycle is 28-30 days, ovulation usually occurs in the middle of the menstrual period, about 14 days before the next period, and the day of ovulation is the day of ovulation. Women have 15-20 follicles each month, but only one follicle usually matures and expels one egg, or occasionally two eggs, which are ovulated by both ovaries in turn. Proper intercourse during ovulation can increase the chances of conception.