The above calculation is based on a straight formula of adding 280 calendar days to the submitted date. This is a generally accepted estimate of birth date (due date) but it is only an estimate, and should not be taken as a guarantee of your child's date of birth. Because most births occur within 10-14 days on either side of this date, this calculation should be taken as an estimation/reference only. Your doctor or obstetrician can confirm your expected due date with you.