Improper use of "Whenever"

I keep hearing a couple of people from Kentucky and Oklahoma say things like, "Whenever I was ten years old". Like they were ten years old more than once. Or, "Whenever I was in High School". This just seems like the word should be "When" in these circumstances. It drives me crazy when I hear this.

This usage, where it means "at an unspecified/uncertain time" is fairly common. I usually hear it (and say it) in a construction more like, "Whenever it was that I first came to...". I don't know if you would also object to this structure.

In terms of being "valid", the dictionary lists:

adv.

1. At whatever time.

2. When. See Usage Note at whatever.

conj.

1. At whatever time that: We can leave whenever you're ready.

2. Every time that: The child smiles whenever the puppy appears.

Surely you say things like "whenever you want" -- this is the same "whenever".

This is a known dialect feature of the American South (but I can't find a reference right now). I don't know that it has a different meaning from "when" in your dialect.