Good evening girls, can you tell me the estimated date of delivery? We…

Good evening girls, can you tell me the estimated date of delivery? We're 17 weeks and 2 days pregnant, we had an ultrasound today and they said it's a boy. Before that at the screening on week 12 and 3 days, they said it was a girl, could they be wrong about the sex at 17 weeks and 2 days?