Jan. 1, 2020 is the beginning of a new year — but is it also the start of a new decade?
Well, that’s up for debate.
While it may seem like a simple answer, disagreement over whether the new decade begins this week or a year later is flaring up on social media.
The answer isn’t totally clear, and it’s a debate that’s popped up in the past between two sides — Team Zero and Team 1. Some people believe the decade begins at Year Zero, or 2020, others believe it should begin at Year 1, or 2021.
What Team One says
The National Research Council of Canada, which oversees Canada’s official time source of atomic clocks, explains on its website that in the Gregorian calendar, there is technically no Year Zero.
That’s why it argues that, for example, the third millennium and 21st century actually began on Jan. 1, 2001.
The U.S. Naval Observatory holds the same position. In 1999 — just before a new millennium was celebrated at midnight in 2000 — the organization did a deep dive into the topic.
It found that years are counted beginning with AD 1. That means a century begins at Year 1 and goes to 100.
According to the American Astronomical Society’s Rick Fienberg, there’s no one definition of what constitutes the official beginning of a decade. But Fienberg did tell NPR radio that the answer seems clear.
“History is clear: because there was no Year Zero, the first decade of the common era (CE or AD) was years 1 to 10, the second decade was years 11 to 20, and the next decade will be years 2021 to 2030,” he said.
“It’s true that ‘the 20s’ — that is, the period 2020 to 2029 — is a decade, i.e., 10 years, but in terms of keeping track of decades from a calendrical (rather than cultural) perspective, the decades are counted as noted above.”
What Team Zero says
However, all this didn’t stop people around the globe from celebrating the year 2000 as a new millennium, century and decade.
That’s because a decade technically just means any 10-year period.
The U.S. National Institute of Standards and Technology — which serves as the country’s official source of time — weighed in on the matter, with scientist Andrew Novick breaking down why the Year Zero argument still carries some substance.
While Novick acknowledged the official calculations begin at Year 1, he noted that in practice, things are different.
“Culturally, people have referred to a decade as a period starting with a 0 and ending with a 9 (1970-1979),” Novick wrote on Twitter. “Make sense? You wouldn’t say that someone born in 1970 was from the sixties, would you?”