Ovulation prediction

Glow says my fertile week started yesterday and that I should ovulate Sept 8, but my other app (which I started using before Glow) says my window starts tomorrow and I should ovulate on Sept 10. I have ovulation strips but I wasn't going to start til tomorrow because of my other app but should I go ahead and start testing?? How accurate is Glow usually with your alls ovulation prediction? Thanks :)