The number of days of menstruation on the 30th is ovulation, which is related to the specific number of days of the menstrual cycle and the regularity of menstruation, so it needs to be analyzed on a case-by-case basis. If your menstrual cycle is regular and you get your period once every 28 days, if you get your period on the 30th and there are 30 days in the month, your next period will be on the 28th of the following month. Usually the day of ovulation is on the 14th day before the next menstrual period, which is around the 14th. And the ovulation period is usually 5 days before and 4 days after the ovulation day, a total of 10 days, so the ovulation period is on the 9th-18th of the next month. However, if the usual menstrual cycle is irregular, the ovulation period is also irregular and cannot be projected according to the above method. You can visit the gynecology department of a regular hospital for ultrasound monitoring of ovulation. If you plan to get pregnant, you can arrange intercourse reasonably during ovulation, which can improve the chance of pregnancy. However, if you are not planning to get pregnant, you need to use good contraception when having intercourse to prevent unwanted pregnancy.