Because this is an MMO, some bending of the laws of space-time is required.

Time moves in accordance with the story, not the server. At the conclusion of the 2.0 main scenario, the date progresses from 5-7UE to 1-7AE by virtue of the victory over Lahabrea (whether this should truly be considered the end of the umbral era is up for debate, but Eorzean politics intervenes). Eorzea has to exist in a sort of time bubble to facilitate this story telling. A mundane year may pass, but it will still be the same Eorzean month of the same Eorzean year until the story moves to progress time. We may get another time-progression event in a future expansion.