Clearly when Bahamut wakes up it will be the 8th Umbral Era. Silly GC Leaders. Also the time in Eorzea is different say to the Garleans and I'd say even more so to people from Othard and lands to the east. As far as we know the Umbral/Astral Eras only effect Vylbrand and Aldenard (Eorzea along with a few islands), but since aether of the planet should effect all other continents as well maybe the other lands suffer if Eorzea does as well. Who knows, we sure won't until an Expansion to other lands.

The GC Leaders said the Seventh Astral Era had begun, in a group setting. So regardless of Bahamut and Odin appearing, I'd say we're in the 7A.E. After all a few civilizations fell during the 6A.E., the Garleans invaded, Primals began appearing in the land and it wasn't considered to be all that bad enough to warrant an Umbral Era. So despite Astral Eras being times of prosperity bad things can and do happen.