Wikia

The Anno Domini is the timeline in which the anime Mobile Suit Gundam 00 and its spinoffs take place in. The term Anno Domini (abbreviated as AD or A.D) is the designation used to number years after the birth of Christ in the Gregorian calendar.

In this "alternate universe" of Gundam, fossil fuels became exhausted and the distribution of fuels became imbalanced. Humanity must rely on three large-scale solar power systems that are in the hands of the three "major powers", and the use of space elevator. Constant warfare around the globe for fuels and energy lead to the formation of a private military organization, called Celestial Being (ソレスタルビーイング), dedicated to eradication of war with the use of four powerful mobile suits called Gundam.

Many fans had noted that it holds similarities to Gundam Wing (Gundam vs. World) and cold war (MAD Doctrine).