For some people, knowing their menstrual cycle and ovulation is important because it helps them better plan their fertility plans. If you have your period on the 13th, then according to the cycle pattern, your menstrual cycle should be 30 days, and your ovulation period should be around the 8th.

In addition, women's menstrual cycles and ovulation periods can also affect their fertility if they want to get pregnant. If you're hoping to get pregnant, you should start planning in the middle of your menstrual cycle and maximize your exposure to sperm. At the same time, care should also be taken to avoid excessive exercise or physical activity during certain periods of the menstrual cycle, as this may affect a woman's menstrual cycle and fertility.

To sum up, it is very important to understand your menstrual cycle and ovulation period, because this will help you better plan your fertility plan. If you are unsure about your cycle pattern, it is recommended to consult a doctor or professional advisor.