I've related these stories on other threads, but I think they might be appropriate here as well.

A couple of years ago, at the local jam session here in the town where I live, someone requested a piece that is apparently considered "traditional" in trad. music circles these days. But the piece was from the renaissance period, and was one I had played many years earlier when I was only playing "early music", which is considered a sub-category of classical.

And I was told by a couple of Scotsmen a couple of years ago a session at Common Ground on the Hill (we thought we were having a "traditional celtic session", but found out otherwise), that Turlough O'Carolan is not even considered traditional Irish music (too newfangled or something?). And if I'm not mistaken, he was composing music in the late 1600s.

So who knows? Maybe some pieces are a lot older than people realize.