Been three days when Jan. 1 knocked on the door of year watchers: Reflecting on the year just gone by and wondering what 2020 had in store ahead.
Many started reflecting on the “past decade” and the new one ahead. “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.
CNN goes further: “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?”
According to CNN, 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 Jan. 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, according to CNN.
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 Dec. 31, 2020, not Dec. 31, 2019.
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 to 1999. It just doesn’t make sense that the year 1990 would be considered part of the ’80s, according to CNN.
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.”