As cycle days can vary from woman to woman (and for me, month to month!) I tested every day from end of a period to the start of a new period to find out where my low/high/peak ovulation days were for the first two/three months until I could determine a rough pattern/no of days for ovulation to focus on for following months. Hormones are most concentrated when passing your first urine of the day so I stuck to first thing in the morning for tests. Based on the apps I was using to track my cycle, neither were that good at predicting when ovulation would occur to what the tests told me. Hope this helps - good luck!