I knew something was off from a young age, but I figured I could "overcome" it. I tried various things, but by the time I was a teenager I knew it was a battle I was unlikely to win. In my early 20s I started going down the road of transition in earnest, I remember setting up a big plan to be "done" with transition by the time I was 30, and I defined SRS as that endpoint. Looking back that was naive, but I did manage it at 32 so I wasn't so off plan.
So I guess you could say my medical transition was from 24-32 but, my social transition and pretransition planning goes back to like 19. I wish I could have started earlier, but I am still lucky to have been able to do it as young as I was.