At some point something happened around I don't know, November of last year, and ever since it doesn't predict my period correctly, nor does it take my changes. Now with a more recent update, every time I try to change my ACTUAL period timeframe from the predicted time, it keeps suggesting the next day as the start date. Every day. For a week at least before finally giving up. I used this app for this, it was SPOT ON, but now it's nothing more than an annoyance, which sucks.