I was 17 when I first heard the term Asperger Syndrome, learned anything about it and autism that was factual and not media dramatizations (Rainman).
Due to my needing accommodations for university, and an incident with a counselor who was determined to convince me that I was merely ADHD, I was officially diagnosed in 2003, when I was 18.
Both my mom and I would have liked it to have been early, before high school. But better late than never, I guess.