At the start of each era, the year resets to 0 (or 1). When 2.0 starts, it's 5 7UE. The fifth year of the 7th Umbral Era. When Bahamut is released in 1.0, the era switched to the 7th Umbral Era.

At the end of the story, the Grand Companies begin a new era: The 7th Astral Era. So, endgame takes place Year 0 (or 1) 7AE.