Dear internet people who flunked basic math. Counting starts at 1. The first decade of the Gregorian calendar started with year 1. The second decade started with year 11. The 203rd decade of the Gregorian calendar starts in year 2021.

When asked about the dispute, Rick Fienberg of the American Astronomical Society says he doesn't think his group has adopted an official position on the matter — but he adds, "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."

10 thoughts on “The new calendar decade starts in year 2021.

  1. @jack @DrOct @khurtwilliams

    Also, I think my programmer friends would say that to assume counting starts at 1 is to guarantee you've just introduced a bug. 🙂

    When it comes to reckoning years, counting does start at 1. Otherwise, children would celebrate their first birthdays after two years of life (and their 0th after 1 year). As @khurtwilliams points out above, the Gregorian calendar doesn’t include a Year Zero, and it would be quite odd if it did. Programming languages typically start with 0 because the decimal system would have to treat “10” as a single digit but for most purposes most of us start counting at 1, not at 0. It doesn’t make a lot of practical difference if people choose to celebrate a new decade, century or millennium a year early but ideally they should know they’re doing so.

  2. @khurtwilliams Correct or not, I'm afraid the argument has been lost. Maybe I'm wrong and the "New Decade" party next December will turn out to be a Rager, but I'm not counting on it.

    Also, I think my programmer friends would say that to assume counting starts at 1 is to guarantee you've just introduced a bug. 🙂

  3. @khurtwilliams I had a longer reply but just removed it because it was unecessarily long and might not have come across the way I wanted (which is friendly!). The bottom line for me is that I personally think calendars are all arbitrary anyway, and can be, and have been changed numerous times. If we as a people want to declare a decade like "the twenties" to be all the years that have a 2 in the tens place then that's fine. If that means someone wants to go back and declare that the first decade of the calendar is only 9 years long... well that's ok too. It's all arbitrary and made up by us anyway, so why not? Anyway, just my two cents. Happy New Year!

    • @DrOct I think that's fair. A decade is any 10 years. I could say my wife and I have been married over two decades and it wouldn't matter when I started counting. But calendar decades start the count at year 1. We are in the 10th year of the 202nd decade of the Gregorian calendar.

      The first recorded zero appeared in Mesopotamia around 3 B.C. The Mayans invented it independently circa 4 A.D. It was later devised in India in the mid-fifth century, spread to Cambodia near the end of the seventh century, and into China and the Islamic countries at the end of the eighth. Zero reached western Europe in the 12th century.

      So perhaps we Westerners are still learning to understand the concept of mathematical zero and counting and I will now start my point of reference for decades at my birthday. I will celebrate the new decade in 2026.

  4. @khurtwilliams I had a longer reply but just removed it because it was uncessarily long and might not have come across the way I wanted. The bottom line for me is that I personally think calendars are all arbitrary anyway, and can be changed and have been numerous times. If we as a people want to declare a decade like "the twenties" to be all the years the have a 2 in the tens place then that's fine. If that means someone wants to go back and declare that the first decade of the calendar is only 9 years long... well that's ok too. It's all arbitrary and made up by us, anyway.
    Anyway, just my two cents. Happy New Year!

  5. @khurtwilliams I would argue since all calendars and systems for dates are arbitrary and made up by humans anyway, we don't have to keep doing something based on when a calendar (that was created hundreds of years after the date it was supposed to start. No one who lived in what has been delcared year 1 knew it was year 1 at the time), decided to begin. The calendar has been updated and changed numerous times, including times that have caused years to change and months to move around. It's up to us when the decade starts. It can be 2020 if we want it to be. And it can end with 2029 if we want it to. Who cares if there was no year zero. There wasn't really a year 1 either. Personally, I think it makes a lot more sense that way. The 20's should include all the years that with a 2 in the tens place, and shouldn't include years with a 3 in the tens place. 😉

    • @DrOct In accordance with the Gregorian calendar, the 21st (twenty-first) century, the current century of the Common Era, began on January 1, 2001, and will end on December 31, 2100. It is the first century of the 3rd millennium. In accordance with the Gregorian calendar, the current decade began on January 1, 2011, and will end December 31, 2020. The Gregorian calendar counts ordinally, there was no year zero, and we are still in the 202nd Gregorian calendar decade.

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