The day of conception refers to the time when the sperm and egg cell unite after sex occurs, and the difference between the week of conception and the day of conception is normally about 14 days. The calculation of gestation week is usually counted from the first day of the last menstrual period, which is the time when the egg cell starts to develop. When the egg cell develops and matures, it will be discharged from the follicle, and it can survive in the body for 12~24 hours, when you have sex at this time, you may be able to conceive. Under normal circumstances the difference between the week of conception and the day of conception is usually about 14 days, which may fluctuate with the menstrual cycle. However, in some abnormal cases, such as irregular menstruation, there is no direct correlation between ovulation and menstruation, and when this pattern is disturbed, it is not possible to clearly determine the difference between the week of conception and the day of conception. If you want to determine the week of pregnancy, it is recommended to go to the hospital in time for ultrasound and other examinations to determine the specific week of pregnancy.