Babies born before due date

I've always thought this and I'm not sure if I'm alone here but I'm curious to see what everyone else thinks or your experiences. I really believe that babies dont come "early" (before they are actually due). I think that there is more likely just not an accurate date of conception. And of course i'm talking about a healthy pregnancy without complications where a baby is born between. 36-40 weeks. Are there any moms out there that knew for sure what the first day of your last period was and still had your baby before your "due date?"