How to know what day you ovulated.

So glow says I had a 33% of the 1st if this month, does that mean its the day I most likely ovulated? Or is it just that that is the better day to have sex, since you should haves sex the day before ovulation for a better chance of pregnancy. I counted from the 1st day of my period to track my ovulation (14 days) and I ended up with the 2nd. Then another app I have said I ovulated on the 3rd. I didnt take OPKs. I should have though. Does anyone have any better idea than I do?