How Old Is Artemis Fowl?

Artemis Fowl is twelve years old and the protagonist of the Artemis Fowl series by Eoin Colfer. Artemis is a 'criminal mastermind'. In the first book, his aim is to obtain a tiny book which is written in a language known as Gnomish.
Artemis wants to obtain the book so that he can translate it in order to obtain some gold. In the first book, Artemis lives with his mother, who is unwell due to his father's disappearance. It is thought that Artemis's father, Artemis Fowl senior, is dead. Artemis discovers in a later book that he is in fact alive.
Artemis becomes friends with a fairy named Holly Short after kidnapping her in the first book. Artemis lives in a mansion (the Fowl Manor) with his servant Butler and Butler's sixteen year old sister, Juliet.
Other recurring characters in the series include Mulch Diggums ( a dwarf), Foaly (a centaur) and Commander Root (a fairy and Holly's boss).

I have done some math with the facts given by Eoin Colfer (i.e., the fact that he was twelve in 2000 or 2001 and his birthday is 0109)
Artemis Fowl was born September first, 1988 or 1989. So this past September he would've turned 18 or 19. Shoot, now I feel really young. :(

He is 12