When Does the New Decade Start?

Is 2021 the Start of a New Decade?

December 30, 2020
Fireworks New Year's Eve

Is the year 2021 the start of a new decade? Or, did it begin in 2020; after all, we’re living in the “twenties.” It’s a simple question, but the answer can depend on the words you use! There are two ways of thinking about this. We’ll explain—and let us know what you think. 

What Is a Decade?

When does the new decade begin and end, anyway? Let’s consider what the word “decade” means. The Oxford Dictionary states, “a period of 10 years, especially a period such as 1910–1919 or 1990–1999.” That’s it.

Note how the dictionary references two decades, both starting in a year that ends in a “0” and ending in a year that ends in a “9.” We do commonly refer to “the 1990s” or “the nineties.” We don’t think of a decade as ending in “1” or as the “ninety-ones.”

However, what may confuse people is that “century” and “millennium” do not follow this rule. Let’s take a century which is a period of 100 years. Based on Anno domini, the year numbering system we use today, the 21st century started on January 1, 2001. In this case, the year ends in a “1.”

Why? Based on our numbering system, Anno domini, there is no year zero. The year 1 BC was not followed by 0, but rather by year AD 1, so we count up from the year 1 AD as in the “21st century.”

Notice that we don’t speak the same way when it comes to decades. Even though the 2020s will be the 203rd decade, we don’t call it that. We call it the “2020s.”

So, Is 2021 the Start of a New Decade?

There is some debate about whether the “new decade” began on January 1, 2020, or will begin on January 1, 2021. To put it plainly: Does the decade begin with a year ending in “0” or a year ending in “1”?

Well, it depends on the context:

  1. Culturally, we say “the eighties” or “the twenties.” In other words, people commonly think of a decade (such as the 1980s, 1990s) as years ending in 0 to years ending in 9. So, 2010 to 2019; 2020 to 2029.  
  2. However, today’s Gregorian calendar counts decades starting with the first year 1 CE. As discussed above, the Gregorian calendar goes from 1 BCE to 1 CE; there is no year zero. In this case, 2021 is technically the start of the new decade.  

Our conclusion? It simply depends on the context of what you’re saying. If you’re referring to ’80s music, we get it. If you’re the US Naval Observatory—in charge of the master clock—the new millennium began on January 1, 2001. 

At the end of the day, astronomy rules the day, and calendars are imperfect. An almanac, by definition, is a “calendar of the heavens.” The Earth will continue to revolve around the Sun, cycling through the seasons.

However you define a decade, let’s just celebrate the start of a new year—especially after 2020—and welcome new beginnings with the year 2021!!

Happy New Year!

About This Blog

Your Old Farmer’s Almanac editors occasionally share our reflections, advice, and musings—and welcome your comments!