There is more misconceptions on calculations of expected date of delivery, your healthcare provider will calculate your gestation age in weeks so that they can give more precise medical care.
The EDD is calculated from the first day of last menstural periods, not from your date of conception as its difficult to predict the date of ovulation.
EDD is calculated by adding 7 days to your date of last periods
(LMP) and adding 9 months to the month or counting 3 months back from your LMP.( which comes to 40 weeks)
EXAMPLE- IF LMP IS 5/09/2023 THEN EDD WILL BE 12/06/2024.
But this method will work only if you had regular cycles previously at least for 6 months.
What you should do if cycles are irregular, then your doctor will advised a dating scan to confirm your delivery date. Even in scans dates are reliable only if done less than 12 weeks of gestation.
Your date will not change as per scans in advanced pregnancy as its not a reliable method and with scan dates your EDD will not change.