Of the many things worth arguing about in America, the number of years that constitute a decade is probably not among them. The word quite literally means “10 years.” But consider historical time, often referred to in decade-based shorthand, and all of a sudden the clear concept of a decade gets blurrier.
Most decades in America have a corresponding social and cultural narrative that’s an uneasy fit in the actual calendar. The ’50s are often stereotyped as an era of postwar domestic prosperity, but the trends cited as proof, such as the growth of the suburbs, reach well into the ’60s. That decade, in turn, cannot tidily hold the massive shifts attributed to it. In her book San Francisco and the Long 60s, Sarah Hill makes the case for two definitions of the era—one spanning four years of counterculture and political upheaval ending in 1969, and another that persists to this day in American attitudes toward sex, drugs, and art. The ’80s, too, spilled over their borders, arguably terminating both politically and culturally circa the dissolution of the Soviet Union and the release of Nirvana’s Nevermind in late 1991.
These are “decades” in the spiritual sense—periods based not on measured time, but on shared temporal perception. In practice, these eras get generalized to calendar decades mostly out of convenience. “The ’60s” is easier to include in a sentence than “the years of intense hippie counterculture, the culmination of the civil-rights movement, and political upheaval over America’s controversial entrance into the Vietnam War, among other things.” And when you say “the ’60s,” people generally understand that that’s what you mean, even if the first five years are a better fit with the ’50s. Decades of temporal perception are rarely neat, and there’s nothing neat about 21st-century America.