How do you KNOW the actual day you ovulated? 🤔

J

So I was tracking my ovulation using opks and I got a positive on CD14, I also had ovulation cramps the same day of the positive opk. That led me to believe that I definitely ovulated on CD 14; however, I read that you typically ovulate 1-2 days after a positive opk. So how do you all know for sure the day you ovulated?