positive OPK then even darker OPK the next day?

So yesterday at 1 PM I got this test, followed by another positive just like it at 5 PM:
And then today at 10 AM I got this one: 
Obviously the one from today is darker, this wasn't even after the 5 minutes. So which day should I consider ovulation, today or yesterday? I know if you get more than one positive you consider the first one your O day, but what if it's even darker the next day?