I use a number of fertility tracking apps but the 2 that have been the most accurate have been <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Period Tracker</a> and Fertility Friend. Both seemed to agree on which day I ovulated based on BBT and OPK's. Just this morning PT decided to up and adjust my O day and I'm curious to get your opinions on which one might be more accurate by looking at my charts. Pictures in comments.