due date change?

So I'm a little confused about my whole due date situation. I was told at my 12 week scan my due date was May 1st, and then at my second ultrasound (anatomy scan) I was told it was closer to April 28th but we would keep it at May 1st officially since it's really just a window and babies come when they want, and the difference isn't that much. I know due dates change all the time but now I'm just wondering should I change my due date on this app and my other <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">pregnancy apps</a>? I count the weeks and days religiously!