This chart is some fun pop cultural proof of periodization: the idea that history is easier to study when we divide it up into discrete, but often arbitrary, blocks of time, like the Gilded Age or the Depression era.
Of course, that's not really how the world works, and it shows when looking at some of the most famous people from different eras.
Intellectually, we might be able to understand that Harriet Tubman and John Wayne lived at the same time. But in our minds, one belongs to the Civil War era, while the other is exclusive to the swaggering cinema of the 1950s.
That may be why no matter how much you stare at the chart above, you'll always be disoriented seeing Jimmy Stewart paired off with Justin Bieber.