So, the way ovulation works is that your fertility window is essentially over. One day before you ovulate? Great. One day after, likely too late. But since it is hard to pinpoint exactly when we ovulate (which lasts about 24 hours of egg being there), and once in a rare blue moon, someone may have a second ovulation --- doctors say there is no 'safe' time to have sex without worry of conception. So, the chance of getting pregnant after you ovulate is zero in a perfect world but since it is nearly impossible to pinpoint exactly when ovulation begins and ends and you could have a second egg, there is always a chance. Small one, but a chance. You can take a pregnancy test 2.5 weeks after and it will be accurate. By the way, I always recommend temperature taking. If you do this, it gives you a bit more insight. Take your temp every morning before you even get out of bed and chart it. You will notice that cycle day one through about midway through the cycle, you have a specific temperature. Then it will go up one degree at that midpoint. This happens after you ovulate. It stays high until you are starting your next period. Then it drops back down to the lower degree of the first half of your cycle. It will stay UP if you are pregnant. If it never drops down to that lower degree and you don't get your period, you will most likely get a positive pregnancy test. So, I liked it because the body doesn't lie even when our brain plays tricks on us when we want to get pregnant.