The Anno Amagium calendar system was established by the Arch Magus, Homer, with the founding of the First Amagium, following his destruction of ancient Athens.

Like most real-world calendar systems, it took several decades and lots of political upheaval before it saw universal adoption, especially in East Asia.

There have been several periods in history when the AA system was motioned to be abolished in favor of another dating system, most notably, the collapse of the First Amagium (which loosely coincided with the fall of the Roman Empire), but ultimately, inertia and convenience prevailed.

An official Anno Amagium timeline is forthcoming, but the serial kicks off in the year AA 2344, which is a period of development that is roughly equivalent to the early 2010s in our world.