Why aren’t we more excited about the ’20s? As in the 2020s?

Is it because we’re still too busy lamenting the end of the Teens? (Wait, did we actually call the years from 2010 to 2019 the Teens?)

We like to think in terms of decades — the Roaring ’20s, the Depression-era ’30s, the war-ridden ’40s. Maybe it helps us remember and make sense of the past. But it takes a while to establish the character of a decade, and it’s often a sloppy thing, spilling over the lip of one 10-year period and sloshing into the first few years of another.

What defines a decade — at least in our collective memory — is events, rather than just the 0’s and 9’s. Some argue, for example, that the so-called swinging ’60s started with the death of President John F. Kennedy in 1963 and ended with the moon landing in 1969.

When you start to examine how we think about decades past, you realize that our understanding is, well, a bit simplistic.

Here’s a quick overview of how we’ve come to view the past 100 years or so, decade by decade:

1890s: In the Gilded Age, robber barons in top hats looked at watches on gold chains while they strode from their carriages to their mansions, batting aside the urchins who had gathered with caps in hand in hopes of a few pennies. The economy seemed to consist of railroads, oil and periodic panics.

1900s: Huh. Aside from Teddy Roosevelt in the White House and the Wright brothers taking flight, this decade doesn’t seem to have stuck in the popular imagination.

1910s: The decade is largely defined by the First World War, which was defined by barbaric trench warfare. The way we liked to tell is that the American GIs showed up, won the war and went home to ticker-tape parades.

1920s: Jazz was invented, and women cut their hair short, smoked cigarettes and voted. Booze was illegal, which led to the rise of gangsters in striped suits who carried machine guns in violin cases. Charles Lindbergh flew to Paris (the second time in the century Parisians would be happy to see a Yank).

1930s: The stock market crash of 1929 brought the Roaring ’20s to a screeching halt. Everyone stopped dancing the Charleston and shuffled through bread lines.

1940s: With a world divided between Allies and Axis, we remember this as another war decade. Women went to the factory and men went “over there,” just as they had for World War I.

1950s: It seemed like it was all cars with tail fins and teens rocking around the clock. Women were back in the kitchen, while their husbands landed good-paying jobs. We loved Elvis, feared Communists and worried about the Bomb.

1960s: The Beatles, feeling groovy and Woodstock figure heavily in our memories. So, too, do the Vietnam War (the first war conducted with a rock ’n’ roll soundtrack), Martin Luther King Jr., Bobby Kennedy and landing on the moon.

1970s: Did everyone have orange shag rugs and polyester pants, or does it just seem that way? Watergate brought down Richard Nixon. Inflation and gas prices were offset a bit by disco and Michael Jackson.

1980s: We wanted our MTV and video games, as well as “Dallas” and “Cheers.” Even though we embraced our material side and declared greed as good, we lived with the fear of a nuclear attack.

1990s: Computers seem to burst on the scene, with everyone logging into AOL because “You’ve got mail!” Bill Clinton wore sunglasses, played the saxophone, and survived impeachment. For years, we were worried about Y2K.

2000s: We never figured out what to call this decade, so sort of accepted “the aughts.” This roller coaster of a decade began with the Sept. 11 attacks, included the Great Recession and lots of cat videos.

2010s: It’ll be a while before we settle on how we remember this decade. Likely to factor into that assessment: #MeToo, video games, superheroes and going viral.

2020s: It’s entirely possible that some technological breakthrough that reshapes society — nuclear fusion, a cure for dread diseases — happens in the ’20s, and almost nothing that everyone natters about on a daily basis will matter at all to historians. That’s the good news.

The bad news: The things that really, really matter, and change everything all at once — well, you’ll know it when you see it.