A moratorium is in effect on adding information from Fire and Blood until December 20th.
True History is a text of the history of Westeros, presumably written by maesters. It suggests that the Battle for the Dawn and the building of the Wall occurred eight thousand years ago, rather than six thousand years. The text states the Andal invasion began four thousand years ago, rather than six thousand or two thousand. True History insists that the children of the forest abandoned the riverlands before the arrival of the Andals, contradicting the legend of Erreg the Kinslayer being an Andal who attacked High Heart. It also suggests that Alyssa Arryn lived four thousand years ago, rather than six thousand according to legend or two thousand according to Maester Denestan's Questions.
A Dance with Dragons
Hoster Blackwood tells Ser Jaime Lannister that the Brackens usurped the riverlands from the Blackwoods as river kings a thousand years before the Andal invasion, according to True History, but the Blackwood family believes it was only five hundred years prior.