Well for starters I have two apps for.perood tracking and ovulation this one and <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> . My <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> I recently put everything to how it was supposed to be ny calculating the days in between from last day to start of next af. It said im 3days late .. as though on the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> it says my period is due the 29th ? Idk which app to go by !!