Why do none of the app line up together?!

Shelby

I have multiple period/<a href="https://play.google.com/store/apps/details?id=com.glow.android">ovulation tracker</a> apps but none of them are in sync.

Glow says ovulation is today.

PreMom(the opk kit Im using) says tomorrow.

<a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Period calendar</a> says the 16th?

this is my opk chart.

So confusing idk when I ovulated or if I have?