i just wanted to know that how to calculate pregnancy date or cenception date like this site https://pregnancycalculator.club/
Sounds like a medical question (and probably not especially accurate).
It is certainly better asked to a doctor, but if you want to know how the calculator works… they use the timelines that doctors use, which using fixed number are a good estimation but mostly not exactly corresponding to reality (and with women that are far away from the average used also greatly wrong) and then do some calculations with those numbers and the dates you enter in the fields and give you the best guess they can give
Accuracy is reached only through the examinations during the pregnancy
thanks, i will research more about this