It is not normal for your period to come 17 days apart. The normal menstrual cycle for women should be 22-35 days, with an average of about 28 days. It is usually within the normal fluctuation range for menstruation to come seven days early or seven days late. A woman’s menstrual cycle is calculated from the first day of the last menstrual period to the day before the next menstrual period. If a menstrual cycle is less than 22 days, or less than 21 days before the onset of menstruation, it is considered early menstruation. Premature menstruation is one of the disorders of dysfunctional uterine bleeding, mostly caused by insufficient luteal function of the ovaries, and usually requires treatment. When menstruation comes 17 days apart, it is possible that it is due to luteal insufficiency of the ovaries. Luteal insufficiency causes early menstruation, and the quantity, color, quality and period of menstruation are consistent and unchanged, mainly due to shortened cycles. Menstruation comes 17 days apart. Another possibility is ovulatory bleeding, which is a small amount of vaginal bleeding that occurs about 14 days before the next menstrual period, that is, in the middle of two periods, and the amount is significantly less than that of menstruation. Ovulatory bleeding is mostly due to a small amount of endometrial shedding caused by fluctuations in hormone levels around the time of ovulation. The bleeding is very small, short and usually does not require treatment.