Every world or campaign setting has a timeline of historical events. Normally this has the format of a year number followed by a short description. For example:
−9800 DR: The Yuirwood was settled by green elves in the aftermath of the Crown Wars.
−6950 DR: The star elves began leaving other elven nations and gathering in the Yuirwood.
−6600 DR: The star and green elves founded the realm of Yuireshanyaar in the Yuirwood.
(Example from Forgotten Realms Wiki)
I wonder if there are generators that can create a random timeline to use it in my own campaing. I tried this generator: http://orfinlir.de/3rdE/historyX.php, but perhaps there are better options.