What year did League of Legends come out?

When did the Mac version of League come out?

 Kayle, Karthus, Mordekaiser, Olaf, Sona, and Yorick

Akali, Evelyn, Kai'sa, Ahri, and Seraphine

 Aphelios, Ezreal, Kayn, K'Sante, Sett, and Yone

The Mageseeker: A League of Legends Story

The Tale of Teemo: A League of Legends Story

How well do you know the history and culture of "League of Legends"?