How old are you, Percy?

As we all know, today is the day we celebrate the birth of Perseus "Seaweed Brain" Jackson. And before we all begin to sing at our worst that endearing song, let's take a moment and think: how old is our beloved Percy? On the Camp Half-Blood wiki, it states that he was born August of 1993, which would make him 20 years old today, but if you do the math, well . . . he was 12 in June of 2005, no? If we take it from there, it means he turned 13 that August, 14 in 2006, 15 in 2007, 16 in 2008, 17 in 2009, 18 in 2010, 19 in 2011, 20 in 2012, and 21 today. Then there's the fact that, no matter how much we want him to be, Percy isn't real, meaning he's kind of stuck in the last place Rick put him, making him still be 16. I'd like to know your thoughts. Is this demigod still a teenager, or is he an adult? 16, 20, or 21? Or is there another answer?