So I posted a few days ago about how accurate the app is. My Husband and I had sex on the last but one day of my Glow-calculated fertile period, it said I had 8% chance of pregnancy. My period was due to start today, again Glow-calculated, but it hasn't arrived so I clicked the 'my period is late' button on my daily log. Now, on the day my Husband and I had sex (the 8% day) it has changed to 33% chance.