Nice catch here. I loooked into the German Version on finalfantasyxiv.com and there it is the same.
"What is Eorzea" say - Umbral (Shadow) Era starts.
and on "Eorzea" it say - Astral (Light) Era starts.


On the English Version "What is Final Fantasy XIV?" it is the same as offical SE website.

And by following "Learn more" it say under Eorzea this:

But in the seventh verse of the Divine Chronicles, Mezaya Thousand Eyes prophesized a less fortunate fate. The "senary sun," or Sixth Astral Era, would indeed end, and the "septenary moon," or Seventh Umbral Era, would cast its shadow upon the land.

Maybe in ARR we start at the end of Umbral Era and in the main Story we go towards Astral Era?

. . .

Now i´m getting headaches . . .