Why did my ovulation date change?

Brittany

Like the title said .. why did my ovulation date change on the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> my ovulation day was supposed to be tomorrow and now it's saying is 2 days from now I've been taking ovulation tests and I think I ovulated on the 9th already.