5k YA to present.
Recorded history generally begins with the rise of agricultural city states in Egypt, Mesoptamia, the Indrus Valley, and the Yellow River in China. These obviously weren’t the first civilizations; just the first for which we have any reliable records.
For GAFT, known history is like a massive setting supplement that we don’t have to pay for. It serves as a handy, encyclopedic guide so that we are not required to make everything up from scratch, and yet there are plenty of gaps that can be filled in by our own imagination, and to our own purposes.
A word of caution then to the rulebook lawyers turned historians - where the game story and established history differ, and you take the trouble to point this out, remember that while we respect the energy you took to actually look that up, we are still, in the end, going to refer you to Rule #1.
Even so, stuff really happened, and while we use that stuff for our amusement, treat it with the kind of respect due from time-travelling teenage superheroes.