Because it's an ESTIMATION. No one can know 100% exactly when your baby is due.

Chances are, your baby is not going to be here on 7/12 or 7/11. A due date is called an estimated due date for a reason. No one knows the exact moment they got pregnant and no one knows when your body will go into labor/deliver that baby.

There is a /- of up to 2 weeks on either side of that date when your baby could potentially show up. Unless you have a scheduled induction or scheduled c-section, no one can tell you when your baby will get here.

A full term pregnancy is 40 weeks. At this moment you are 37.5 weeks pregnant based on a 7/12 due date. On Saturday you will be 38 weeks. On the next Saturday you'll be 39 weeks. Then on the 12th, you will be 40 weeks.