CNN

When does the decade begin and end anyway?

Dec 28, 2019, 5:29 PM | Updated: Jan 3, 2020, 3:03 pm

The question of when exactly the current decade ends and the new one begins seems to come up every ...

The question of when exactly the current decade ends and the new one begins seems to come up every time the year on the calendar moves from ending in 9 to ending in 0. Photo: Shutterstock via CNN

(CNN) — As January 1, 2020, approaches, everyone is reflecting about the past decade and the new one that awaits. “Best of the decade” lists are everywhere. #10YearChallenges are all over social media. And people are eagerly gearing up to celebrate the end of the 2010s.

But there’s a slight problem.

We might be celebrating a year too early, at least according to some people.

The question of when exactly the current decade ends and the new one begins seems to come up every time the year on the calendar moves from ending in 9 to ending in 0. It came up in 1989. And in 1999. Then again in 2009. And now.

So is January 1, 2020, really the beginning of the decade? Or does it, in fact, begin a year later, on January 1, 2021?

Let’s dive in, shall we?

It depends on who you ask

When exactly the decade begins and ends all depends on who you ask.

The US Naval Observatory, the agency that maintains the country’s master clock, tackled this question in 1999 as people debated when the new millennium would begin. According to the astronomical dating system through which it measures time, the observatory stated that the new millennium would begin on January 1, 2001.

The Farmers’ Almanac, America’s centuries-old go-to for weather predictions, astronomical data and more, takes a similar position.

“As you think about New Year’s resolutions, here’s one we should all make together: resolve to insist that decades begin with the year ending in the numeral 1 and finish with a 0,” an article on its website reads.

The Farmers’ Almanac insists on this because of how years are numbered in the Gregorian calendar, the system in official use throughout most of the world. The anno domini era, or the common era, begins with year 1 on the Gregorian calendar.

In 525, a monk known as Dionysius Exiguus set out to determine the date of Easter and created a system of labeling years based on the date he thought Jesus Christ was born (a date that’s considered historically inaccurate today). But he didn’t account for the years before the birth of Jesus.

That was done in 731 by a monk known as the Venerable Bede. Bede counted the years before Christ and established the BC era, but he didn’t include a year zero in his calculations. Which means that the year before 1 AD was 1 BC.

Because there’s no year 0 in the calendar, the first year was complete at the end of year 1, not at its beginning.

By that same logic, the first decade in the calendar was complete at the end of 10 CE, or 10 AD.

Which means, according to the Farmers’ Almanac, that the end of this decade is December 31, 2020, not December 31, 2019.

We talk about decades differently

Those technicalities, however, don’t change the fact that as a society, we seem to have collectively determined that decades begin in years ending in zero and end on years ending in nine.

After all, it makes sense.

When we think of the 90s, we think of the period from 1990-1999. It just doesn’t make sense that the year 1990 would be considered part of the 80s.

Plus, it’s more satisfying to celebrate big occasions like the start of a new decade in an even-numbered year, a phenomenon that psychologists call “round number bias.” Waiting until 2021 to celebrate the new decade would feel anticlimactic.

That’s why Konstantin Bikos, lead editor of TimeandDate.com, says that both definitions of when the new decade begins are correct. No need to cancel your end-of-the-decade party.

“There’s two different ways of categorizing 10 years,” he told CNN. “It could be from the year ending in 0 to the year ending in 9, or the year ending in 1 to the year ending in 0.”

It comes down to how we talk about time spans.

Bikos agrees that centuries and millennia always start with years ending in 1. Those time spans are typically referred to as numbered entities counted up from the year 1 AD, as in the “21st century” or the “third millennium.”

Decades are categorized by year numbers. Even though the 2020s will be the 203rd decade, no one ever calls it that. It’s just called the 2020s, or the 20s.

So when it comes to decades, Time and Date is flexible.

This definition of a decade is so ingrained in popular culture that the people at Encyclopaedia Britannica never really considered the possibility that a decade could begin in any other year besides one ending in zero.

“I love the question because it has never really occurred to me or any of us at Britannica to be concerned about it,” J.E. Luebering, executive editorial director at Encylopaedia Britannica, told CNN. “That may underscore that we’re humanities-leaning perhaps than science-leaning. But the consensus here is that we’re a bit mystified by the debate.”

Does any of this matter?

Astronomically, not really.

The only thing that year numbers really signify is the number of times that the Earth has completed a full revolution around the sun.

“In terms of counting millennia or centuries or decades, it doesn’t really matter,” Bikos told CNN. “It’s a man-made system. It matters in terms of categorizing time spans and talking about time spans. But the 203rd decade is, in astronomical terms, no different than the decade before or after.”

Others point out that the system on which our calendar is based is riddled with inaccuracies and inconsistencies, making the whole discussion arbitrary.

“In the grand scheme of things, it seems like a lot of technicalities on something that hasn’t been very consistent,” Luebering said.

Time and Date adds that the debate about the new decade is only relevant right now in the Gregorian calendar. Though that’s the calendar that most Western countries abide by, there are a bunch of other calendars that use entirely different year numbers, like the Jewish calendar, the Islamic calendar, and the Hindu calendar.

“So, while the Gregorian calendar is the system officially used around the world, this goes to show that our year count is nothing more than a random fabrication, which is ultimately based on the ideas and religious fervor of a 6th-century monk,” Bikos wrote in an article about the start of the 21st century.

And that year count is based on a date that scholars now believe is wrong.

“What’s more, Dionysius Exiguus based the beginning of year BCE 1 in the Julian calendar, the predecessor of today’s calendar system, on a religious event—the birth of Jesus—which not only lacks astronomical relevance but is also based on religious lore and, as such, a rough estimation at best.”

So there you have it, folks. Time is an illusion.

We want to hear from you.

Have a story idea or tip? Send it to the KSL NewsRadio team here.

CNN

Outside of the Yale University Law School is pictured on September 27, 2018 in New Haven, Connectic...

Zenebou Sylla, CNN

Some New England universities, including Yale, break $90,000 barrier for total tuition cost in upcoming school year

(CNN) — Several New England universities and colleges, including Yale, have reached a pinnacle of at least $90,000 for undergraduate tuition and costs starting this fall. Yale University, Tufts University, Boston University (BU), and Wellesley College are among a few private institutions that will top this year’s costs for tuition, housing and other expenses, according to […]

18 hours ago

Former senator Joseph Lieberman...

Jake Tapper, CNN

Former Sen. Joe Lieberman dies at 82

Former Democratic vice presidential nominee and Sen. Joe Lieberman has died, according to a statement from his family.

23 hours ago

Doughnuts are displayed for sale at a Krispy Kreme store on February 13, in Austin, Texas. Krispy K...

Ramishah Maruf, CNN

Krispy Kreme doughnuts are coming to McDonald’s

The Krispy Kreme doughnuts will be available nationwide at participating restaurants by the end of 2026, after a phased rollout beginning later this year.

1 day ago

The Federal Trade Commission is investigating TikTok for its data and security practices, two sourc...

Brian Fung and Samantha Delouya, CNN

FTC investigating TikTok over privacy and security

The probe is yet another complication for the social media platform. It's already facing the threat of a potential US ban or a forced divestment from its Chinese parent company.

1 day ago

A hand holds a tablet stamped with "MF," standing for mifepristone....

CNN

Study shows how self-managed abortion became more common, as Supreme Court abortion drug hearing looms

Medication abortion has become increasingly common since it first became available in the United States two decades ago.

2 days ago

People place flowers at a memorial outside Crocus City Hall in Moscow on Sunday following Friday's ...

Sophie Tanno, Eve Brennan, Anna Chernova and Darya Tarasova, CNN

Thousands gather in Russia to mourn victims of concert hall attack

Russia on Sunday held a day of mourning after at least 137 people were killed in a terrorist attack on a concert venue in Moscow.

3 days ago

Sponsored Articles

Mother and cute toddler child in a little fancy wooden cottage, reading a book, drinking tea and en...

Visit Bear Lake

How to find the best winter lodging in Bear Lake, Utah

Winter lodging in Bear Lake can be more limited than in the summer, but with some careful planning you can easily book your next winter trip.

Happy family in winter clothing at the ski resort, winter time, watching at mountains in front of t...

Visit Bear Lake

Ski more for less: Affordable ski resorts near Bear Lake, Utah

Plan your perfect ski getaway in Bear Lake this winter, with pristine slopes, affordable tickets, and breathtaking scenery.

front of the Butch Cassidy museum with a man in a cowboy hat standing in the doorway...

Bear Lake Convention and Visitors Bureau

Looking Back: The History of Bear Lake

The history of Bear Lake is full of fascinating stories. At over 250,000 years old, the lake has seen generations of people visit its shores.

silhouette of a family looking over a lake with a bird in the top corner flying...

Bear Lake Convention and Visitors Bureau

8 Fun Activities To Do in Bear Lake Without Getting in the Water

Bear Lake offers plenty of activities for the whole family to enjoy without having to get in the water. Catch 8 of our favorite activities.

Wellsville Mountains in the spring with a pond in the foreground...

Wasatch Property Management

Advantages of Renting Over Owning a Home

Renting allows you to enjoy luxury amenities and low maintenance without the long-term commitment and responsibilities of owning a home.

Clouds over a red rock vista in Hurricane, Utah...

Wasatch Property Management

Why Southern Utah is a Retirement Paradise

Retirement in southern Utah offers plenty of cultural and recreational opportunities. Find out all that this region has to offer.

When does the decade begin and end anyway?