The standard unit of periodisation in pop culture history is the decade. The Eighties. The Fifties. Each of these terms for ten-year spans of history instantly evoke a whole web of distinct associations and aesthetics. The Roaring Twenties: flappers, bobbed hair, the Charleston. The Swinging Sixties: hippies, beehives, Volkswagens, sexual liberation. We know, at some level, that January 1940 is barely any different from December 1939, and yet these calendrical boundaries are the joints at which we cleave our popular conception of history.

My vague impression is that this is a modern thing. I am familiar with the personalities of decades all the way back to the 1920s, but past that my impressions of decades become more indistinct. The 1910s had World War I, and the 1900s were kind of vaguely old-timey in a patriotic town-square brass-band sort of way, and the Gay Nineties had old-moneyed aristocrats and cute little waltzes about bicycles, but before then, what? Decades before that just kind of bleed together, and we have period names of a coarser granularity—the Gilded Age, the Victorian Era, the Old West, the Antebellum, the Regency Era. Then this just fades into an indistinct haze of centuries—the Eighteenth Century, the Seventeenth Century, and so on.

Why is this so? Is it just a consequence of these centuries being far enough away from us that we’ve lost a grasp on what their decades felt like, or did history actually move more slowly back then? Was 1470 as distinctly different from 1460 as 1970 was from 1960? If you could ask the 1923 equivalent of me to imagine the 1840s, would the visions be as clear as I can imagine the 1940s (Victory rolls, shirtwaist dresses, jitterbugs)?

If it really is a function of distance (and not of the speed of history), should we expect to see the 1920s and 1930s fade from pop culture over the next twenty years? Will they fall off the treadmill and slide into an oblivion of obscurity? Will they stop feeling like distinct decades and merge into one hazy Interbellum period?

Have they already done that? I get the impression that for many people my age, everything before the Fifties has been shaved off into Old History—treatments of popular music start with the birth of rock-’n’-roll, and Instagram models doing the era-progression-montage thing begin with polka dots and poodle skirts.

A century from now, will our understanding of the decades of the 20th century be lost? The Nineties as a teenage hormone-ridden grungeland on the brink of the information superhighway? The Eighties as shoulder pads and big hair and jazzercise and pastels? The Seventies as a lone gas station on a stretch of interstate, a hobo sleeping under burnt-out neon signage, oranges and browns?

And what of our newly minted decades in the 21st century? Strangely I feel that they don’t have personalities as distinct as their predecessors. Do we need to give them distance before they become more sharply defined in retrospect? Or are we entering some sort of stasis? Or is the media landscape so fractured now that there is no one single vision of 2020s culture?

Has the decade as a unit of periodisation stopped being useful?

Was it ever useful?