Sounds like a to-die-for must-have for every modern stone-age family!![]()
That wasn't intentional

The problem with setting specific dates to the tech tree is the tech tree is not a historic timeline. Its a guide to HOW (not when) different techs were invented. A player can beeline to different techs and get some earlier than others. Thus slowing and neglecting when other techs are invented.
Likewise in real life some techs are discovered at different rates depending upon the civ. For instance in the East was much more advanced than the West during the European Dark Ages. Likewise the Americas were very far behind on the tech tree compared to the Europeans that came.
In short setting X to mean a specific date is impossible to do. The best we can do is say these groups of techs are invented during this era and even then we fudge things if a tech straddles 2 different eras.
Okay.