When it comes to single player games, there’s nothing wrong with trying out some cheats and seeing what happens. Sometimes you just gotta cheat, and Sketchy's mod is here for you. You can then play up to the normal end date of 1453, almost a millennium of Crusader Kings 2! The mod can be found on Paradox’s official forums or the Steam Workshop.
This is where When The World Stopped Making Sense steps in: The mod follows the migratory period following the collapse of the Western Roman Empire in 476, and allows players to choose a starting date any time between 476 and the year 600. A copy of Crusader Kings 2 with the Charlemagne DLC allows gamers to play from 769 all the way up to 1453, but some history buffs may be interested in an even earlier starting date.