Which of these OPK test day is accurate?

I've tested Sunday, Monday and Today (Tue). I'm haven't gotten a flashing smiley. Only blank circles and solid smileys. On Sunday when I got the solid smiley. I took the test strip out and tossed it in the trash. The smiley never went away. It is still lit now, 3 days later. I figured it's defected and purchased a new one. Which day do you guys think is the real/exact ovulation day? I'm leaning more towards today now since both are solid smileys but I'm not sure. I'm still new to this. Please help.