Pregnancy is counted from the first day of the last menstrual period, for example, if the last period is 01/01/2020 – 05/01/2020, then 01/02/2020 is 31 days of pregnancy. The medically calculated number of days of pregnancy is two weeks longer than the actual time of conception. The medical calculation of the number of days of pregnancy is usually expressed in terms of weeks of pregnancy, seven days being one week, one month being four weeks, and the entire pregnancy period being 40 weeks of pregnancy or 280 days, with the due date being the number of days in the 40th week of pregnancy. To calculate the due date, the month of the first day of the last menstrual period minus three or plus nine, and the date plus seven, for example, if the last menstrual period is 01/01/2020, the due date is 08/10/2020. Most people will give birth naturally at around 40 weeks of pregnancy, and a birth two weeks early or two weeks late is natural.