But I read a post by Ancient History and Frank Trollman, and they were talking about how most of the elven population was only 18 when the Tirs were founded.
And AH and FrankTrollman are, of course, wrong.
If it refers to the post I think it does, Frank Trollman pointed out the oldest living regular elves were just 18 when the Sinseareach tribe was founded in the Salish-Shidhe in 2029, and 24 when Tir Tairngire was established. They also remarked those elves would be 43 years old at the time the
Tir Tairngire sourcebook is set, making the point on how elves never retires from their job positions meaningless. All of which is true (check, 2029-2011=18, 2035-2011=24, 2054-2011=43).
There were "spike babies" born before that would be older, but
Tir Tairngire is written with the assumption that their existence was a secret and that the entire number of those Sean Laverty could find in North America would fit into a big house. The
Tir na nOg sourcebook, on the other hand, makes Liam O'Connor birthdate in 1979 is a public fact as early as 2015.