A friend of mine once made a competition, where we should guess the due date of his first born (many month before the event). I did the sensible thing and call

A friend of mine once made a competition, where we should guess the due date of his first born (many month before the event). I did the sensible thing and call up the biggest hospital in my country, talked to the head maternity doctor, explained the situation for her and asked what she would guess. She laughed and said the in the 30 years she had the job no one ever asked her this (the competition thing). She said that for since it was going to be a first born, her guess would be 2 weeks after the date my friend was suggested by his doctor. The child was born 1 week before the due date. So she was off by 3 weeks. So not an easy task to make a accurate Due Date Calculator it seems