3 apps..

I have three apps for tracking periods/ovulation. <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Period Tracker</a>, Glow, and Ovia. Two (glow and ovia) say I ovulate the 8th but <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Period Tracker</a> says I ovulate the 10th. Which should I believe?

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