With a July 30 due date, the time of conception could be between November 4 and 13 of the previous year. If a woman has a regular menstrual cycle and is due on July 30, the approximate date of her last menstrual period is October 23 of the previous year. Ovulation occurs on the 14th day before the next menstrual period, which can be between November 4 and 13 of the previous year, and most of the time when conception occurs lies during ovulation. The expected date of labor can be calculated by the time of the last menstrual period. Clinically, it is rare to judge the last menstrual period by the expected date of labor, and even rarer to judge the time of conception. The expected date of delivery can be calculated from the last menstrual period, and then the ovulation period can be calculated from the last menstrual period, so as to calculate the time of conception. It is necessary for women to go to a local public professional medical institution and under the guidance of a professional obstetrician and gynecologist to determine the expected date of delivery and the time of conception.