When can you start complaining about the youth of today?

[AJS-]

As per the title.
I'm in my early 30s and it seems odd to hear people who are significantly younger than myself moaning about the youth of today.

So what seems like a decent age to you?

[AJS-]

Fort Jefferson said:

If you're only 30, how can anybody be significantly younger?

I suppose that depends on your interpretation of significant

I would say a 21 year old is significantly younger than me, and at 21 you are the youth of today, hence have no business complaining about them.