House of the Dragon Season 1 takes place over decades. Characters live, age, and die with every episode that passes by. Wars come and go, villains rise, and heroes fall, and the Targaryen dynasty stands true and proud all the same. Yet the Targaryen dynasty is not where Westeros' history begins and ends. While there have only been two shows spelling out the conflicts in the region, the Game of Thrones timeline began long before the events of House of the Dragon.
Source：https://www.cbr.com/house-of-the-dragon-westeros-history-explained/
