Normally, most women have a menstrual cycle of about 28-30 days, but some women may experience an early or late menstrual cycle, but the early or late cycle is within one week. As the ovaries ovulate earlier or later, it causes the menstrual cycle to move forward and backward, as long as the time of moving forward and backward is within one week, it is a normal menstrual cycle and does not need special treatment. This is related to the time of ovulation, because women do not ovulate on a fixed date, so there will be occasional advance and occasional postponement of the normal performance.