So confused!

So I have two apps I use to track my period and ovulation, etc., I just started using Glow, and the other I've be using for years. Glow says my fertile window started on the 29th and my ovulation day is Tuesday, February 2nd; my other app says my fertile window starts today and my ovulation day is the 5th of February. How confusing!! Which calendar do you think I should go by, and fyi I'm bd on both calendars ovulation days, plus most of my fertile days, just to be safe lol