The Timeline in The Inheritance Games Universe Confuses

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What year do The Inheritance Games and The Grandest Game series actually take place in? I thought the books followed chronological order in real life, but if they do, then shouldn’t the characters be older by now? Like, shouldn’t Jameson be around 23, Avery be 22 turning 23, and Xander around 22 as well? Shouldn’t most of the characters be around 22–25 by now? Why does it feel like Nash and Libby are the only characters actually aging while everyone else stays the same age?