In The Last of Us: Part II, Joel plays and sings the Pearl Jam song Future Days. The problem with this? In the universe of The Last of Us, the song could never have been released, as it was scheduled for a month after Outbreak Day.
This led several fans to suggest that there is a timeline error in the game, something that director Neil Druckmann has now come forward to deny. Using his Twitter account, Neil Druckmann remembers the song was actually first released on Youtube, via a live Pearl Jam performance. That actually happened before the Outbreak Day, and as such, explains how Joel knew about the song.
And there you have, no timeline error.