I got diagnosed at 34. The diagnosis profoundly changed my life. Suddenly my experiences had an explanation. It was very validating.
There have been so many times in my life where people have noticed something wasn't quite right with me. The first time was when I was about 2 years old. It was thought I had some kind of developmental delay and hearing impairment. Teachers also noticed and many of the psychiatrists I interacted with during my adolescence. Back then ASD was unheard of so I got a diagnosis of personality disorder and schizoaffective disorder.