[safety1st]

None of the best programmers in the world are in their 20s.

If you want to be the best in the world it does help to start young.

But if you just want to be really good, you can start any time. In a pursuit like programming there is some benefit to being young, having those 'crackling synapses' which help you think fast.

But there's also some benefit to being old - the longer you work the more you build up a library of solutions in your head. Every time you solve a problem it gets easier to solve it (or a problem like it) again.

Which is the bigger advantage? Hard to say. But programming isn't like basketball. No programmer peaks in his 20s. So maybe that's your answer.

[noobermin]

And it isn't chess. A lot of programmers who are good start in their teens or younger may be but it isn't really something you are groomed for, at least I know no one in my personal life who is like that. The fact that passion brings you a lot of the way vs. professional training or just prodigy as a youth (think olympics, gymnastics, basketball, chess, e-sports, etc) means that really you can start any time.

Like others are saying, the only difference where age might matter is life circumstances, it's less about mental faculties (you don't need a quick reaction time to hack unless it's a competition may be) beyond logical reasoning, which people of any age can master.