Does each decade start in the “zero” year or the “one” year?

Photo by color line - CC-BY

Photo by color line - CC-BY

Strictly speaking, every year starts a new decade. For example, 2007 started the decade of 2007-2016. A decade just means ten years. However, for many cultural purposes (such as to group events together) a series of decades is designated according to a regular pattern.

For most of the population, the significant decades are those beginning in a year that ends in zero, and running through to include the year that ends in nine. For example, 2010 to 2019 inclusive would be a decade.

Some people are sticklers for correctness. They remind us that there is no year zero in our calendar—the year called 1 CE (AD 1) directly follows the year called 1 BCE (1 BC). Therefore, the argument goes, the first decade ran from 1 CE to 10 CE, and all subsequent decades must follow the same pattern.

It’s all a bit theoretical, because our current calendar system didn’t exist back then. It was designed centuries later. Nevertheless, those who support the idea that decades must start with years that end in one can be quite insistent about it.

Those who don’t feel constrained by the lack of a year zero tend to prefer the convenience of defining each decade as those years that only differ in their last digit. This allows the convenience of referring to the decades by their “tens digit”: the nineties, the eighties, the seventies, the sixties, the fifties, the forties, the thirties, the twenties, and the tens. But what of the decade before the tens? It’s sometimes called the “noughties”, a somewhat jocular term.

Feel free to celebrate the start of the decade whenever you like. But take a tip from me: the “new decade” parties in in January 2010 will be more lively than the “pedants’ parties” in January 2011.

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  • Larry says:

    The (we) pedants only get bitchy about counting from the beginning of the calendar, knowing that there was a first year that was half finished after the first six months = 0.5 of the first year. Think of the X-axis of a graph.
    After another six months, the first year was completed, and then it was the year one, like a child’s “first birthday”, actually the first anniversary of its birth. It was a decade old on its tenth “birthday” and began its second decade.
    We are always living in the year following the number of our last birthday or the year on our calendar. Again in decimals, today (Dec. 13) we are about 0.95 into the year 2010 already = 2009.95 AD.

    But I’ll still go to anyone’s new decade party at the end of the year, since any ten year period can be defined as a decade.

  • T.C. says:

    It is of my opinion that decades do indeed begin on the ‘0’, because when a child turns “ten” years old, he has been alive for ten years, thus beginning a new decade of life. It is, in fact, the same concept pertaining to years, as in the beginning, once 10 years (AD) was reached, a new decade was thus begun.

    I could write more, though it may border on trolling, so I’ll refrain.


  • James McKee says:

    that is the best explanation ever.

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