A little decadence

By Phil Plait | December 31, 2009 7:00 am

Quite by accident, just the other day I found myself embroiled in a controversy on Twitter of my own making. I made an offhand mention that the decade would be ending in a few short days. That seemed obvious enough to me, but apparently not so to many others. What ensued was something of a firestorm of people, many of whom disagreed with me. However, I maintain that I was right all along. Here’s the scoop.

My claim is that December 31, 2009 — today, as this is posted — is not just the last day of the year, but the last day of a decade. Now, I don’t mean that in the trivial sense that any moment is the last moment of the past ten year period — you can always talk about the last ten years that end at any time.

I meant, and still mean, specifically the first decade of the 2000s. That does in deed and in fact end today.

What people were arguing over were things like centuries and millennia, and how there was no year 0, and therefore the last day of the decade is actually December 31, 2010. But that’s not relevant because we don’t measure decades the same way we do centuries.

Certainly, the last day of the 20th century was December 31, 2000. In that case, there was no year 0, so the first year of the 1st century ended on December 31, 1 A.D. Doing the math, it’s easy to see that 1999 more years needed to elapse to end the 20th century, and so its demise was on that last calendar day of 2000. January 1, 2001 marked the first day of the 21st century.

But we don’t reckon decades like that. We refer to them by the tens place in the year’s numerals: the 70s, the 80s, the 90s. And since we do, clearly, today is the last day of the decade we will call the aughts or zeroes or whatever.

Actually, looking at this now, it seems to me that centuries are more formal, with an actual method of naming them, whereas decades are more of a nickname, a handy handle to use when referring to a time period.

Also, you wouldn’t say that 1990 was part of the 80s, would you? I think it’s clear that December 31, 1989 was the last day of the 80s, just as December 31, 2009 is the last day of whatever term we’ll wind up using to refer to the first 10 years of the 2000s.

Confusing this a bit is that we might refer to something happening in the 1900s versus saying it happened in the 20th century. Those terms are synonymous, barring the year of 1900, which was in the 19th century, and 2000, which was in the 20th century but not in the 1900s.

If we did reckon decades the same way as centuries then a point would be made that the decade ends in 2010. But we don’t, and in this case there truly is a year 0: the year 2000. So once again, the first decade of the 2000s ends today.

A couple of people pointed out that this means the first decade in our calendar only had 9 years: AD 1 – 9. I suppose that’s true, and so it’s not really a decade then in the strict definition of the word. But since we’re not using a rigorous naming convention, and references to decades are more like nicknames. Plus, who talks about the first ten years of our calendar that way anyway?

Confusing this even more was the case someone made that when you are 30, you no longer say you are in your 20s (unless you’re lying). But all during that last year, when you say you are 29, you are actually living your 30th year on Earth. After all, when we say a baby is 1, really they have already been around 12 months. We change the number after the fact, so when you turn 30 you’ve already lived out your 30th year. The whole time you are 29, you’re plowing through your 30th year.

Perhaps it would lessen the issue if, when asked how old you are on your birthday, instead of saying "I am 30," you say "I have just completed my 30th year." I suspect that won’t catch on, however.

Still, be all that as it may, when you are 29 you are still in your 20s, and when you turn 30 you ain’t.

The lessons here are many fold. One is that, and pardon my repetition, the first decade of the 2000s ends today. A second is that people are still terribly confused about how to delineate centuries. A third is that this can be generalized to people being confused on how we delineate time.

Fourth is that this is all arbitrary and a bit silly. But we do make rules, and sometimes those rules have to make sense, and sometimes it’s fun to talk about them even when it means some people disagree.

And fifth? People shouldn’t argue with me on Twitter. At least not until the next decade starts.

And if I may indulge myself, one final thing:

Happy new year!

And happy new decade. May the 10s and teens treat us all better — and may we make them better — than the aughts.

MORE ABOUT: calendar, decade, new year

Comments (139)

  1. PaleGreenPantsWithNobodyInsideThem

    The last day of the century was 12/31/1999. There was no year 0, or 1, or 2 or 55. It’s all meaningless. I prefer to make parties happen when all the numbers change. I am unanimous in this and anyone who disagrees is a self-important snob.

  2. This 1st decade has been termed the “noughties” in the UK which I find quite amusing.

  3. Phil, I’d feel less embarrassed for you — and for everyone else too — if you were all arguing about something that actually mattered. Like, for example, where we’re all supposed to get our Glau/Dushku fix once Dollhouse bites it next month.

  4. RL

    Summer Glau….

    Bring back TSCC!

    Now that’s a cause worth fighting for!

  5. If we get really, really, really technical, the debate over year zero is rather muddled. Since the Gregorian Calendar was accepted in what was labeled 1582 and had issues with things like leap years which had to be properly accounted for later, and what exactly January 1, 1 AD was and how it was determined was a matter of scholarly debate for a while, using the purist argument of a lack of year 0 AD is not really as precise as it may seem at first glance…

  6. Simon

    Everyone should read Questioning the Millennium: A Rationalist’s Guide to a Precisely Arbitrary Countdown by the late Stephen Jay Gould. Especially the last paragraph.

    I miss Gould!

    IMO anyone who doesn’t like naming 12/31/2009 as the end of the “Oh-No” decade should join me in partying (like it’s 1999) until 12/31/2010.

  7. You see, this is why I actually have a Year Zero in the calendar for the stories I’m writing. The event that triggered the switch (Before Cataclysm/After Cataclysm) happened mid-year, and that year is considered to be Year Zero, Zero BC, Zero AC, or the Year of Cataclysm. So one year can be refered to in four separate, but correct ways.

    Makes it much easier in my world, and milleniums, centuries, and decades do end on 0 years.

  8. Actually, I do consider 1990 as part of the 80s, but not for reasons pertaining to year zero.

    The cultural gestalt that we think of as, say, the 90s, didn’t really coalesce until 1992ish or so. And this is true for pretty much every decade. In 1982, we were just coming out of the 70s, and the fashions and popular culture that constitutes the 80s was just starting to appear.

  9. Nomen Publicus

    I, for one, blame those darn theists for not paying more attention in maths classes.

    We are all grown up now, so why not slot a year zero between -1 and +1 (biased on the -1 side so positive years do not change.) A small change that would eliminate all future arguments about centuries and millenniums.

  10. I agree. In his review of the film A HARD DAY’S NIGHT, Roger Ebert remarks that the world was essentially still in the 1950s at the beginning of the 1960s. And he marks the start of the 1960s with George Harrison’s 12-string chord which opens the song “A Hard Day’s Night”.

    In English, both “the nineteenth century” and “the 1800s” exist, though the former is perhaps more common. In others, like Swedish, only the latter (“1800-talet”) exists.

    Someone mentioned Gould above. I’ve read all (yes all, even the big ones) of his books. I highly recommend TIME’S ARROW, TIME’S CYCLE. A whole book about the question whether time is an arrow or a cycle. (As Groucho Marx said, time flies like an arrow, fruit flies like a banana.)

  11. Decades are a cultural measurement. The Eighties, then, are generally reckoned to be the period from Reagan’s inauguration (20/01/81) to the collapse of the Soviet Union (25/12/91), thus neatly encompassing the entire period of big hair, shoulder pads, pastel colours, Protect & Survive, New Romantics, and everything else that means the Eighties. So, yes, 1990 was in the Eighties. It certainly didn’t feel like the Nineties (plaid shirts, grunge rock) when we were living in it. It’ll take another ten or twenty years before we can decide what were the defining moments of whatever decade this is.

    In terms of indexing from zero or from one, decades and centuries should be reckoned the same way, both distinct from terms like “the 1900s’ and “the 90s”.

  12. Cliff Moore

    @Nomen Publicus

    Wait, wait, woah there. Civilization as we know it was almost destroyed when Pluto’s classification was changed, and now you want to go adding a YEAR to the calendar? Are you *trying* to set the Pope on fire? 😛

  13. Blaise Pascal

    I am perfectly willing to accept that today is the last day of the ’00s and the last day of the first decade of the 2000’s, but not the last day of the first decade of the 21st century. There have been only 9 years in the 21st century, so it can’t be a proper decade yet.

    But really, we refer to decades the way we do as a short-hand for various social, political, and cultural things going on. The 30’s dominated by the Depression, the 40’s by WWII and it’s immediate aftermath, the 50’s by the beginnings of the post-war boom and a streak of social conservatism highlighted by thinks like “Leave it to Beaver”. the 60’s by the Vietnam war, the rise of Rock&Roll, hippies, etc, the 70’s by Watergate, post-Vietnam, the oil crisis, the 80’s by the final throws of the Cold War, the feeling of prosperity, “Greed is Good”, the 90’s by the rise of the WWW, the dot-com bubble and crash, and the ’00s by the War of Terror and post-9/11 feelings.

    I tend to view such decades as having transitions with significant events which either cause or represent a sea-change in how society works. I could make a case (when talking to an astronomer or space buff) that July 21st, 1969 was the end of the ’60s, because that’s when we got to the moon and the American public then promptly stopped caring about the space program. But I could make compelling cases for Kent State, Watergate, the Fall of Saigon, and Nixon’s resignation, too. All, in my opinion, are better choices than Dec31 1969 or Dec31 1970.

  14. stogoe

    Going off of what pajh has said, by my reckoning the (cultural) Nineties didn’t end and the (cultural) Naughties didn’t start until September 11, 2001.

  15. Just glad this decade is over and hoping the next one better.

  16. PaleGreenPantsWithNobodyInsideThem

    Oh for Zarquon’s sake. You people have put too much thought into this. Pop your Champaign and Drink in the new decade and stop worrying.

  17. Eighthman

    Totally agree. There’s nothing wrong with referring to the ’00s as “the decade.” C’mon, instead it’s supposed to mean “the first decade of the 21st century”? Really? Sorry, it’s not.

    It’s a shame our society is so obsessed with meaningless odometer flipping (um, 2012?) and breaking records (i.e. the [hottest/coldest/windiest/whatever] day in the past [long time]).

  18. a lurker

    Phil is right. This is the end of the decade sometimes called the “noughties.” Just like 1999 was the last year of the “nineties.” However, if he said it was the end of the “201th decade” then he would be wrong as that goes on to next year.

    PaleGreenPantsWithNobodyInsideThem: “The last day of the century was 12/31/1999. There was no year 0, or 1, or 2 or 55. It’s all meaningless. I prefer to make parties happen when all the numbers change. I am unanimous in this and anyone who disagrees is a self-important snob.”

    Anyone who says that the end of the 20th Century was 1999 is just plain wrong. It is not snobbery, it is just the facts. I have no problem if you want the 1999’s being the end of the century called the “nineteen hundreds” though. But if you call it the Twentieth Century then you are wrong.

    Meanwhile I might say that yesterday was the end of the Blah-Blah Century. As I defined it, I can pick any 100-span that I wish. But if I name a century based on the Gregorian Calendar than I am obliged to obey its conventions and thus I can’t pretend that the First Century did not start on year 1.

    Maybe it would be nice to have a year zero, but it would be confusing unless we officially ditched the Gregorian Calendar. Maybe instead of 2 BC could become 1 BPM that is “before Ptolemy of Mauretania.” Wikipedia says that he was born on 1 B.C. which will now be the zeroth year of the Year of our Ptolemy (YP).

  19. bubba

    I don’t know that I agree with Phil. I have argued with people in the past about how we don’t count from 0 – 9, but from 1 – 10. I don’t believe the events of a decade determine the start and end of it (I think that’s a whole different scale), nor do I count the year 2000 as the start of the 21st century.

  20. rob

    bah! you are all a bunch of geeks (c’mon, admit it!) and ought to be using hexadecimal. the year 2009 is really 0x7D9, so the new hexade won’t occur until 0x7E0, or another 7 years.

  21. Jamey

    Sixth: Our language is replete with ambiguities and ill-defined terms. Heck, we don’t even have a good definition of a computer! Are all of those “supercomputers” with dozens of rack-mounted servers connected by ultra-high-speed networks really single computers? If not, how are they different from quad-core PCs with four cores tied by an on-die network? If so, isn’t the Internet just one big computer and nobody has their own computers any more?

    And yet, we want computers to read our minds. Look at the huge number of assumptions and minor misunderstandings we make every day. Look at the fight over gay marriage, and the desire to have “civil unions” which are supposed to be the same thing, except not…

    I think we probably don’t need to go as far as becoming lawyers, but I think we do need to admit that it’s not the computer’s fault that natural language understanding and machine translation are such difficult problems.

  22. Perhaps it would lessen the issue if, when asked how old you are on your birthday, instead of saying “I am 30,” you say “I have just completed my 30th year.” I suspect that won’t catch on, however.

    Well, it has in other languages. The way you say “I am 30” in Spanish and French, for example, is “I have 30 years.”

  23. Gus Snarp

    But you aren’t 30 years old until you have lived thirty years. That shouldn’t be confusing.

    Traditional ages in some parts of east Asia have you at 1 from the moment of birth, and your age advances every new year. So if you are born just before the new year you end up being 2 before you have lived a year.

  24. Paul

    Last night, I just finished chapter 1 of Death from the Skies (Xmas present), in which you stated “don’t make me lecture you about how there is no year 0″…. Only to come across this post today…

  25. “I have just completed my 30th year.”

    That’s very Spock-like. I’m sure the Vulcans had a much more sensible calendar.

  26. It’s ‘Naughts’, Phil… 😉

  27. What happened to popular culture trumping science (ala “kph”)? 😉

    The way I see it, either the first century of this arbitrary year counting system had only 99 years, or the 20th century came up short by one year. Take your pick.

    I prefer to go with the latter, since the end of the 20th century was the first time ‘popular culture’ was powerful enough to trump ‘science’ (see Gould – Questioning the Millennium: A Rationalist’s Guide to a Precisely Arbitrary Countdown).

    When the odometer rolls over to all zeros on the end, is when the masses will take extra special notice. Not the following year when a “one” gets tacked on.

  28. Phil, technically, we still have 90 years left in the aughts — ‘010, ‘011, … 😉

  29. Tim

    I got into this same conversation with my wife in the car a few days ago. I told her that the decade doesn’t end until next year. She aske me if I thought 1980 was the last year of the 70’s. Then she said even if I were technically right, I should not go around correcting people because I would just end up looking like a jackass.
    That kind of wisdom is why I married her…

  30. Jamie

    Hmm I’m not sure on the whole “how old are you” argument: You’re not 1 until 12 months after you’re born: sure you are living out your 1st year, but you are not 1 until that year is up. At 3 months you are 3/12 or 1/4 of a year old, etc. So at 29 and 3 months you are only 29 and 1/4 years old. So when someone asks how old are you and you reply “I’m X” you are correct you are X years old (and some change) you aren’t replying that you are living out your Xth year.

  31. Christoph K

    regarding describing one’s age.
    in poland the actually say “i finished the 30th, 35th, etc(whatever the age is)”
    Skończyłem 30 lat. Although there is also the form “I’m … years old”

    A Happy New one to everybody!
    And Farewell International Year of Astronomy!

  32. Thank you for writing this. Have a Happy New Year!

  33. Confusing this a bit is that we might refer to something happening in the 1900s versus saying it happened in the 20th century. Those terms are synonymous, barring the year of 1900, which was in the 19th century, and 2000, which was in the 20th century but not in the 1900s.

    The definitions overlap to within 1%. Close enough for government work. (-:

    Isaac Asimov’s Chronology of Science and Discovery, a year-by-year timeline of scientific achievements, marks the “early twentieth century” as beginning in 1895, with Roentgen’s discovery of X-rays and Becquerel’s of radioactivity.

  34. Nemo

    2010 is the year people will start commonly saying “twenty-ten” instead of “two-thousand-ten”. Although just the other day, I did hear someone say “twenty-oh-nine”, which sounded quite odd.

    In fact, it will probably be the last time people commonly use “thousand” in pronouncing the current year name until the year 3000, unless we change epochs.

  35. John

    Some called the last decade the “aughts”, but I prefer to think of them as the “Oh-Ohs!” It was a pretty much “Oops!” kind of decade.

  36. 8. t3knomanser Says:

    Actually, I do consider 1990 as part of the 80s, but not for reasons pertaining to year zero.

    The cultural gestalt that we think of as, say, the 90s, didn’t really coalesce until 1992ish or so. And this is true for pretty much every decade. In 1982, we were just coming out of the 70s, and the fashions and popular culture that constitutes the 80s was just starting to appear.

    This is approximately what I was thinking while reading the blog post. I was watching NUMB3RS (on DVD, burned from DVR – episode Old Soldiers) and one of the characters said that D.B. Cooper was ‘in the sixties’, when it was actually 1971. Often a less than photographic memory will place an event ‘in a decade’ when it is actually in the next ‘official’ (either 0 or 1 start) decade, but the way we think of decades flexes because there are no real cultural landmarks (that can be considered universal) that decide when one decade ends and another begins.

    Anyhow, have a Happy (and Safe) New Year.


  37. Torbjörn Larsson, OM

    What is this “we” thing?

    First, we absolutely don’t “measure” centuries as an interval, we define them as events with an interval in between. As a measure a decade long interval can start anytime. But there are also calendar decades defined for obvious reasons.

    Second, our definitions are completely arbitrary. I, like most others, celebrated the passing of ‘our’ duomillenium the night of [tick-tick-tick] 2000-01-01.

    Not because we didn’t know how to count on a clock, but because we did. And of course since we could also especially celebrate the night of [tick-tick-tick] 01-01-01, as we knew how to count on a calendar as well.

    Oh, and Happy Naught Year!

    It’s ‘Naughts’, Phil…

    He!Considering the calendar ambiguities, maybe we should refer to them as “The Naughties”?

  38. Chris

    I’ve seen comparisons to ordinal vs. cardinal numbers – one vs first. I think it’s definitely worth asking whether we’re comparing like things or if we’re comparing ‘five’ to ‘seventh’.

    Specifically our language is oriented around natural numbers (you have 3 chickens in the yard or you don’t) and doesn’t handle fractional units well. If a fox got to your chickens and you have 2 living chickens and dead bits of a third, do you have two chickens (round down) or three (round up)? That’s an exact analogue to whether somebody is 30 (round down) or living their 30th year (round up). Formally centuries round down but informally they round up (meaning the 21st Century for everyone but historians started on 1/1/2000) as do decades. None of us were around in 1 BC so we don’t really care that the next year would be called 1 AD centuries later.

    BTW -culturally- the 21st Century started with the election/appointment of George Bush. It’s hard to say whether it’s the date of the election (the start of uncertainty) or the date the Supreme Court stopped the process (the start of deep questions about the validity of the results), but in either case it sets up 9/11 and its aftermath. Imagine a world where President Gore was in office and already knew about (and took seriously) the CIA warnings about OBL. He might not have been able to stop an attack, but who thinks he would have invaded Iraq or be defending torture?

  39. Erasmussimo

    Pascal programmers count from 1. C programmers count from 0. Which side can prove its method to be correct?

  40. giffy

    @1 Agreed.

    I prefer to think that the first century was just short changed a year. Same with the first millennium. It sucks for them, but not for me who gets to celebrate more appropriately. Welcome to the second decade of the 21st Century in the 3rd millennium since the day we arbitrarily fixed the calender to!

  41. GeneralMusings

    The calendar as we know it went from 1BC to 1AD with no transitional year 0 (zero). It would seem to me that given that years 1- 9 do not constitute a proper decade, then one would have to include year 10 for there to be a proper decade. That would then need to be continued through all subsequent decades, centuries, and millennia. Therefore, the last day 20th century was December 31, 2000 and the first day of the 21st century was January 01, 2001. The year 2010 will be the last year of the first decade of the 21st century. The year 2011 will be the first year of the second decade of the 21st century

    But what the hey… Any excuse for a PAR-TAY!!!

  42. Brad

    @22, 31.

    Not only is “I am 30” expressed in Spanish as “Tengo 30 años” (lit. “I have 30 years), but in fact there’s also an expression very close to “I have just completed my 30th year.”

    To say “I turned 30 yesterday” in Spanish, one would say “Cumplí 30 años ayer,” which is literally “I fulfilled/accomplished 30 years yesterday.” It might not catch on in English, but it’s firmly entrenched in Romance.

  43. PaleGreenPantsWithNobodyInsideThem


    Actually, it went from 4bc to 1ad (estimated) and we lost 11 days in the 1500s sometime.

  44. Carlos

    We should just switch everything to base-12 and start all over. Base-12 makes a lot more sense – neatly divisible by 2,3,4,6 rather than just 2,5! At the store and the bagel shop we would buy a neat 10 eggs and 10 bagels. Best of all we would have to deal with the decade/century/millennium end confusion 20% less! Maybe we could even genetically engineer an extra finger in each hand to make sure children learn to count properly. Happy new year all!

  45. PaleGreenPantsWithNobodyInsideThem


    The Sumarians had base 60 for the same basic reason. They didn’t have a 0, though.

  46. All of this pales in comparison to the really important question, which is what do we call the next year? I’m all in favor of twenty-ten, though there’s those weirdos out there who will use two-thousand-ten. 😉 Of course then there’s the short form made popular by Colbert: ‘010!

    Happy New Year, everyone! 😀

  47. PaleGreenPantsWithNobodyInsideThem


    Arthur Clarke’s book 2010 has always, in my world, been pronounce 2 thousand 10. I think I prefer twenty ten, but I don’t think it’s going to happen.

  48. GeneralMusings

    @ 42:

    Okay, but our current calendar starts from year one, not year zero. Eleven missing days do not constitute a year.

    **goes off to find an open bar**

  49. jamiegroots

    Who cares. All i know is that i get to see the second half of doctor who tomorrow. Dam bbc

  50. I use the term “the zeroies” myself.

    “The Naughties” is a nice name/pun too, but as the only people I know who use the term “naught” for zero are the “Beverly Hillbillies,” I’m going to stick with something that requires less explanation…

  51. Brian S.

    There are Pascal programmers left?

    In any case, it’s my birthday, so I’m partying no matter what.

  52. It’s all arbitrary and meaningless anyway. However, I reject any arguments comparing age or “odometer flipping” to calendar events for the simple reason that ages and odometers flip at the end of a completed unit, whereas calendars flip at the beginning of a unit yet to be completed.

  53. Jamesonian

    The problem is not one of mathmatics or metrics, my exceedingly over-educated friends, but one of semantics. A decade is a unit of measure not culture, so please refrain from trying to convince yourselves that a decade can consist of more than ten calendar years. But– and here’s where the semantics enter into play– the term “decade” does not specify which ten years, i.e. the years 1999– 2008 constitute a decade, yes? OK, so a decade does NOT need to be defined by the “tens” number as Phil suggests. It could be, but it doesn’t have to be. So here’s my suggestion: give up referring to the end of the “decade” and just refer to the end of the”aughts” because that’s just what it is. No one could justifiably complain about that.

  54. Well said, Jamesonian.

  55. a lurker

    “Arthur Clarke’s book 2010 has always, in my world, been pronounce 2 thousand 10. I think I prefer twenty ten, but I don’t think it’s going to happen.”

    Of course that might be an artifact that it was a sequel to a movie pronounced “Two Thousand One.” Maybe if Stanley Kubrick had used “Twenty Oh One” we would be saying the names of the nine years after 2000 differently and we certainly would pronounce Clarke’s 2010 novel and the movie adaptation differently.

    The strange thing is that I, like most people, call 2005 “two thousand five” and yet I call 1905 just as I did before the turn of the century as “nineteen oh five.”

    Any linguistic historians know how this was handled the 18xx-19xx transition? How did most people living in 1905 pronounce the name of the year? And when 1910 came, was there any conflict between calling it “nineteen hundred and ten” (or “nineteen hundred ten”) and “nineteen ten”? Of course it might be the case that “nineteen hundred and” sounds to an ear of an English speaker more clunky than “two thousand” and thus the habit of calling the current year in the format of “[xx] [xx]” might go into decline for a century until “two-thousand one-hundred and ten” or “twenty-one hundred and ten” start becoming a mouthful. In any event we might be in an linguistic experiment. Some linguist might start collecting data how people and the media start pronouncing “2010” when the year actually comes tomorrow. If all the current events shows say “xxx for twenty-ten” instead of “xxx for two-thousand ten” or vice-versa it could tip the balance.

  56. Yojimbo

    I think the sensible thing is to celebrate the end of the decade tonight, and then do it again next year. Twice the parties, and all the bases covered.

  57. GeneralMusings

    @ 49

    I thought that Doctor Who: The End of Time, Part Two was scheduled for Saturday evening. Tomorrow is Friday. Didn’t realize that there was a Dr. Who marathon on BBC America tomorrow. Will have to mark that on my calendar.

    I’m going to miss David Tennant. He’s been the best Doctor since Tom Baker.

  58. Sean

    I’m reminded of the three year old I met who stumbled around our house proclaiming “I’m two!” to any adult foolish enough to sit still for five seconds or more.

    Phil, I agree with you. Further, I’ve been referring to this decade as the “aughties”, but really, really like the term “naughties”. It just fits.

    Happy New Year!

  59. NewEnglandBob

    Never mind the calendar. The last day of the decade was the day before Barack Obama was sworn in. It ended the worst decade since the surrender of Nazi Germany.

  60. Strangel

    Well, I say we’re not going to Jupiter so who cares what year or decade it is? We could just start calling it “the 4th year of the Consul Robert Gates and the 2nd year of the Consul Barrack Obama.”

  61. phensley

    No year 0? But of course their is! Especially on an Astronomy blog: Astronomical year numbering follows the dating convention of Julian year 1 BC=0. Other dating conventions, such as ISO 8601, Buddhist, and Hindu calendars include a year 0.

    Of course year numbering is arbitrary, but a calendar in which the first century AD had 99 years makes a mockery of language and logic. Why not choose one of the many superior year numbering conventions available? That way, the year 2000 really is the first year of the millennium, the century, and the 201st decade.

  62. Happy Celebration of another successful orbit. Nothing from some book by some chap happened to this planet this time around.

  63. Supernova

    I’m with Yojimbo: admit the ambiguity and just party both years. But I can’t believe no one’s brought up Julian dates yet. If you want to be totally rational about it, we’re just going from 2455197 to 2455198, so what’s the big deal?

  64. Nora

    Yeah, in Spanish they have that very concept of birthdays. The actual word for “birthday” is “cumpleaños” which basically means “completing a year.”

  65. Dark Jaguar

    My solution: Let 1 BC be Zero AD, and let 1AD be Zero BC. There, now we have a year zero, and we can finally stop acting all snooty about millenium switchovers. It’s true that we don’t decide on decades the same as millenium and centuries, but that’s always been an annoying inconsistancy to me. Heck, since we don’t have a year zero, going on down the list, it “shouldn’t even be the year 2009”. But no one makes that argument. So heck, just let the year zero thing GO, and let’s define centuries and millenium based on the actual digits too. Is that really so hard? What does it hurt to do it that way?

  66. Gus Snarp

    @Chris Swanson, PaleGreenPants, and a lurker – There’s a website: http://www.twentynot2000.com/

  67. Some chap wrote a book?

  68. Ernie in Berkeley

    Just postulate a year zero, with length zero, and all will be well.

  69. Kirk

    Even if Glenn Beck agrees with you, you still may be correct.

  70. CB

    The only sensible solution is to renumber the past… stick a year zero in there between 1 BC and 1 AD, and adjust all of the BC dates… 1 BC becomes 0, 2 BC becomes 1BC, etc. Sure some history books will be off a bit, but we take that stuff with a grain of salt anyway.

  71. I find it odd that someone who’s so pedantic and precise about how the solstices/equinoxes should mark the middles, and not the beginnings, of the seasons, (despite the climate hysteresis in most of the populated world) would be so imprecise as to bracket the calendar decades based on how we conveniently refer to them.

    What’s good for the goose is good for the gander, I say! If convenience rules the day, then let the solstices/equinoxes mark the beginnings of the seasons!

    Not that any of this matters.

  72. “decade: n. 1. a period of ten years: ‘the three deades from 1776 to 1806.’ 2. a period of ten years beginning with a year whose last digit is zero: ‘the decade of the 1980’s.’ 3. a group, set, or series of ten.”

    -The Random House Dictionary of the English Language, Second Edition Unabridged, Random House, 1987, p. 515

  73. Adam

    I have no problem with short changing the first decade. If we concider the year of Christs birth year 1 AD and the year prior year 1 BC we have negative and positive integers with no zero separating the two. So if we are willing to agree to get rid of the zero year we can agree to let the first decade only have nine years.

    Heres another way to resolve it. Since BC stands for Before Chraist it has a hard end date being the birth of Christ. But AD translated the year of our lord is not a fixed date. Thus we can, for conventions sake, make year 1 start with Jesus’ first birthday and the 12 months prior are year 0 just as any baby’s first year would be.

  74. i’ve learned that, in greece, when someone says he’s 30 years old, he means that he’s currently living through his 30th year. an american would say she’s 29.

  75. Ken

    Balderdash. The last day of the 20th century was December 31, 1999.

    No, there was no year 0. But there was a a year 1 BC. (It came right before 1 AD) Doing the math, it’s easy to become an insufferable pedant, but I think you know where I’m going here. January 1, 2000 marked the first day of the real 21st century.

  76. Alan in Upstate NY

    The argument that 2010 is part of the current decade is strange. Would people say they are still in their 20s when they hit 30?

    Clear skies, Alan

  77. Renee Marie Jones

    “Certainly, the last day of the 20th century was December 31, 2000. In that case, there was no year 0, so the first year of the 1st century ended on December 31, 1 A.D.”

    Sorry, Phil. It’s not that simple. From Wikipaedia:

    “Year zero is not used in the widely used Gregorian calendar, nor in its predecessor, the Julian calendar. Under those systems, the year 1 BC is followed by AD 1. However, there is a year zero in astronomical year numbering (where it coincides with the Julian year 1 BC) and in ISO 8601:2004 (where it coincides with the Gregorian year 1 BC) as well as in all Buddhist and Hindu calendars.”

    There ARE systems that have a year zero: the ASTRONOMICAL year numbering system for one. Shame on you :-)

  78. Jeffersonian

    “we don’t measure decades the same way we do centuries”

    “A couple of people pointed out that this means the first decade in our calendar only had 9 years: AD 1 – 9. ”
    As our calendar hadn’t been invented yet, it doesn’t matter except as a thought experiment. Makes the point moot, since the argument is about usability.

    @pajh :
    “decades are a cultural measurement. The Eighties are…the period from Reagan’s inauguration…encompassing the entire period of big hair, shoulder pads, pastel colours…”
    America is the only culture that uses the calendar?

    Cultural tastes are not part of a argument. You could name hundreds of cultural memes that last 15 years or 5 years. “Decade” is a unit of measurement, not a description of culture.

    @Nemo Says:
    “I did hear someone say “twenty-oh-nine”, which sounded quite odd”
    I hear this all the time. Isn’t this common?

    @GeneralMusings Says:
    “The calendar as we know it went from 1BC to 1AD with no transitional year 0 (zero).”
    The calendar wasn’t around for that to occur. We could decide to start the calendar over but we still wouldn’t start with zero.

  79. Chris

    In the real world, the origin of number lines starts at zero. Time counts (especially when doing physical time series) start at zero, initial conditions always seem to imply “t=0”. I have yet to see anyone start a timer for a race, soccer game or anything else at anything but zero. Nor have I ever seen anyone say that their newborn child is one year old (though it seems that is standard in other countries, perhaps they are still using Roman Numerals).

    I have also recently updated my programming skills, it was at first awkward, but I got into the swing of things for designating the first location in the array as Array[0], instead of Array[1].

    It is amazing that since the invention of “zero” that people still want to perpetuate a several century old error. Possibly because Zero was a dangerous idea (actually, there is a book called Zero: the Biography of a Dangerous Idea, by Charles Seife, which I am currently reading).

  80. Huron

    I second #41.

    You’re absolutely wrong, Phil. First decade went from 1-10, not 1-9. Thus, this decade goes from 2001-2010.

    Do you consider someone that is 10 to be in their teens? No, thus 2010 is the last year of this decade, and 2011 is the first year of the next decade.

    I demand that you retire from blogging until such time as you acknowledge the errors of your ways in matters relating to time. To consider 2010 to be the start of a new decade is a barbarous practice.

    A letter to the editor of the Times from January 1, 1900 shall also destroy your post:

    “Sir, The 1900th year A.D. commences on the day this letter will, I hope, appear in The Times. The dictionaries tell us that the word century simply means hundred. Until 1900 years have elapsed the 19th century of years cannot end. And until the 19th century of years has ended, the 20th century of years cannot commence. Therefore the 20th century of years cannot commence until a year hence. And, therefore, the year A.D. 1900 is not the commencement of the 20th century; 1901, so designated, is the first year of the 20th century. Chevreul lived over a century. But he was not a century old until he had completed his 100th year. He did not commence his second century until he commenced his 101st year. So we shall not commence our 20th century until we commence out 1901st year — a year hence.”


    Most disgraceful, Phil, most disgraceful. My respect for you has gone down significantly.

  81. Michael Swanson

    What I like about Phil’s post on this subject is that it’s funny enough, absurd enough, and sarcastically pedantic enough to show that it doesn’t %$#^%$# matter.

    It’s like arguing over the PRECISE start of the Renaissance. Like some cobbler named Ezio was pounding a nail into a shoe in Florence in 1396 when epiphany struck. “Gee. I suddenly feel all different. Almost…I don’t know…reborn!”

    Or let’s go tell a Chinese guy that the new decade starts or doesn’t start tonight precisely at 12:01AM. He’ll say, “What are talking about? The new year doesn’t begin until the 28th of next month?”

    And wouldn’t it make more sense for the damned thing to take place on a solstice or equinox anyway? After all, wasn’t the earth was created on October 24th at dusk, 6014 years ago? 😉

    Have an arbitrarily happy New Year!

  82. Huron


    Your argument is faulty. Comparing the start of a historical period, which any historian will acknowledge can not be precisely determined, to the start of a new year, decade, or century, which the Royal Observatory at Greenwich will tell you can be determined precisely, is most illogical.

    “In the Gregorian Calendar, which we use, there is no year zero and the sequence of years near the start runs as follows; …, 3BC, 2BC, 1BC, 1AD, 2AD, … Because there is no year zero, the first year of the calendar ends at the end of the year named 1AD. By a similar argument 100 years will only have elapsed at the end of the year 100AD. Since 2000AD is the 2000th year of the Christian calendar, it will be the last year of the 2nd millennium. So the 3rd millennium and the 21st century will begin at the same moment, namely zero hours UTC (commonly known as GMT) on 1 January 2001.”

  83. Chris

    Great article and great discussion, but does it really matter if you are celebrating the end of the noughties of the end of the first decade of the 21st century. Just go out and have fun because, after this one, there are only 2 more New Years to go. As we all know that the world will end on 21 Dec, 2012.

  84. RawheaD

    The technicalities, even if you could argue there are in this case, doesn’t matter, because like it or not, nitpickers, nobody in their right minds are going to be wrapping up the past decade (e.g., Best Rock Album of the Decade, Best Horror Flick of the Decade, etc.) at the end of 2010. And insomuch as the term “decade” is colloquial, how it is actually used is all that matters.


  85. RWPhoto

    It all comes down to agreeing on the definition of your terms, something which should always take place before posing arguments.

  86. Anders

    Since it was mentioned, I have to say that in Swedish we do have the expression “det nittonde århundradet”, meaning the nineteenth century, although it’s not as common as “1800-talet”, or “the 1800s”.

    Having said that, I agree completely with Phil. Decades get their names from the digits in the year, so now we enter into the 10s, not the last year of the 00s (whatever that will eventually be called – I don’t think anyone quite worked that out for the 1900s; I do like the noughties though)

  87. GeneralMusings

    I’m right, everyone who doesn’t agree with me is wrong. 😉

    @RWPhoto (86)

    Why ruin a perfectly good argument with logic?

    **Tries to flag down the beer tender to get another round**

  88. Eric TF Bat

    It’s important to be inclusive. That’s why I accept that 31 December 1999 was the last day of the Millenium (note misspelling). That’s for the people who are illiterate, innumerate or sufficiently grumpy that they’ll call people snobbish for having a better education and more interest in accuracy over gut instinct. For the rest of us, 31 December 2000 was the last day of the Millennium.

    And yes, that decade was the Noughties, and it ended last night. Now we’re into the Tenties. If you were naughty in the Noughties, will you be tense in the Tenties?

  89. Alan in Upstate NY

    Huron wrote, in part…
    Do you consider someone that is 10 to be in their teens?


    Would someone who is 30 be in their 20s?

    An inappropriate example too. The teens are from 13 to 19. No one considers either 10 or 20 to be part of the teenage years.

    Clear skies, Alan

  90. Anders

    The ‘teens’ stem from the words thirTEEN, fourTEEN and so on. Someone who is 11 is not in their teens, so that is an exception.

    I don’t consider someone who is 40 to be in his thirties. The words for decades all stem from the words, not from the chronological distance from a mythical deity

  91. Anders

    btw (and I don’t consider this to be OT since it was mentioned :) David Tennant seems to be an all-around good guy, not just as Dr. Who. He was on QI in the last episode, and didn’t do too badly. Phil, if you want a copy, send me an email :)

  92. Phil is logical and correct in his analysis, and for party purposes I will uphold his “decadent” reckoning. Personally, however, I reckon the decades culturally and politically, which means some comprise more than ten years, while others were cut short — and some even overlap, depending on the context. Thus, the ad-hoc mess of time-keeping:

    60s: From JFK’s inauguration to Altamont Free Concert. (Some friends say Kent State.)
    70s: From “Nixon goes to China” to Disco Demolition Night
    80s: From Thatcher’s election to collapse of USSR
    90s: From Bill Clinton’s election to Bush v. Gore
    00s: Bush/Cheney (Two zeros. Need I say more?)
    10s: From Obama’s election night to ? (May all who read this live long enough to find out, for better or worse. Happy 2010!)

  93. davem

    You’re all wrong, of course, since the introduction of the Gregorian calendar was accompanied by the loss of 12 days. So we have to wait for the 13th Jan to celebrate the true new year.

    So we might as well call it whatever we please, since none of us is being at all accurate…

    As to naming the new year, all I’m hearing on BBC TV is ‘twenty-ten’. At long last; I never could stand that long-winded ‘two thousand and nine’ stuff.

    ..Oh and happy new Year!

  94. Mooney

    “And if I may indulge myself,”

    Too late.


  95. Michael Swanson

    @ #81 Huron

    Yeah, my Renaissance reference didn’t really apply.

    But I do contend, even as an empiricist and a lover of science, that there a few things that don’t need to be categorized or defined so rigidly. 10, 2000, these are nice big, easy round numbers, and when it comes to marking the end of a decade or a century in celebration we needn’t be so pedantic. We’re just people, and the difference between 1999 and 2000, or 1399 and 1400 seems like a big deal. It’s why you never see anything for $100 – it’s always $99.

    Our calendar is such a mess anyway. 7 day weeks, 28, 29, 30 and 31 day months, 24 hours days, and year that is 365 and 1/4 days. Leap seconds! We’re not taking measurements for the sake of engineering space shuttle carburators here, we’re talking about an arbitrary date in an arbitrary calendar. (I heard in my childhood that Jesus, he of questionable historicity, was actually born in 4 B.C.!) And if tomorrow starts a year with an arbitrary number, and it’s a nice round one, well then why not a hearty Happy New Decade!

    Me? I probably won’t even stay up until midnight.

  96. Nemo


    Arthur Clarke’s book 2010 has always, in my world, been pronounce 2 thousand 10. I think I prefer twenty ten, but I don’t think it’s going to happen.

    Are you kidding? There’s no way “twenty-ten” isn’t the majority pronunciation by the end of the year. And I’d bet on much greater than majority, much sooner than the end of the year. Any amount of money.


    “I did hear someone say “twenty-oh-nine”, which sounded quite odd”
    I hear this all the time. Isn’t this common?

    Not in my experience. In fact, I think it was the first I’d ever heard it for that year. But it will become the dominant form, starting next year.


    Actually, it went from 4bc to 1ad (estimated)

    What are you talking about? 1 B.C. comes directly before 1 A.D., by definition.

  97. Jay

    The only time “There was no year zero” is relevant is when people are talking about a sequential order of blocks of time. 2nd millennium, 21st century, 201st decade.

    But we are not talking about a sequential order of decades. The Nineties, The Eighties, The Aughts, these are just nicknames for a specific period of ten years (aka a decade).

    1988-1997 is a decade
    1989-1998 is a decade
    1990-1999 is a decade
    1991-2000 is a decade
    1992-2001 is a decade

    The Nineties is simply a nickname we give to 1990-1999. The Aughts (or whatever becomes common) is a nickname given to 2000-2009. Nothing more, nothing less.

  98. This is just yet another instance of the evil of counting from one. If everyone counted from zero like we computer geeks do, there would be no problems. For example, an octave in music is really SEVEN steps from the tonic, so it should be called a heptive. Then music would be more “hep” :)

    Oh yes, and it bothered me even as a child, that 12:30 pm came an hour after 11:30 am. Why would 12 switch to 1 a whole hour after am switched to pm? This problem, too, would go away if all the clocks used zero instead of twelve.

    As for decades AND centuries, it’s totally arbitrary, as others have said. Nobody actually knows whether Jesus existed, and if he did we certainly can’t be sure when he was born. That being the case, surely we should use the simplest definition possible? Ockham’s Razor, you know? In other words, the century began on 2000-01-01 (yes, I think the British and the Americans both have dates wrong. yyyy-mm-dd ftw!) and the new decade begins on 2010-01-01.

    So there.

    Now have a mince pie and a drink of what you fancy, and a happy new decade to you all!

  99. That’s it. Linear time, I am DONE with you!

  100. Buzz Parsec

    No, I’m right and everyone else is wrong! :-)

    Okay, measuring time is time-like. Since this is a sciency blog, we should go on to measuring things that are space-like. In particular, anyone care to explain the chains used in (American) football? Is this or is this not the most ridiculous method of measuring space ever invented? You take a stick and walk across a field and then plant it at an arbitrary location (your best guess at where the ball was on the previous 1st down.) Then you take a 2nd stick attached to the 1st by a 10-yard chain, and plant that approximately down-field from the 1st stick. Then you compare the location of the 2nd stick to the place that the referee arbitrarily placed the football after the preceding play, either where the ball was when its possessor’s knee touched the ground, or where the ball was when the player went out of bounds, or any of several other equally random decisions, and then the entire outcome of the game depends on the result. (I know lots of readers of this blog aren’t familiar with American football; aren’t you sorry for what you are missing?)

    Then, there’s the way the “distance traveled by the Space Shuttle during it’s most recent mission” is measured… Arrggghhh!

  101. tesstricks

    Funny, using “the aughts” to describe the decade that will soon pass/pass in a year is based on, what Rebecca Mead of the New Yorker calls, a “linguistic error.” “Aught” is a corruption of the word “naught,” which means “nothing, nothingness, zero, cipher.” Aught originally meant “anything, all, EVERYTHING” (m-w.com, caps mine). It’ll be interesting to see what we’ll end up using. While naughts is more correct, aughts could be the more popular term – which is okay when you consider that language changes constantly. And because language changes constantly, any of you could be right about what constitutes a “decade” and any person’s idea of what a “decade” is could become the norm in the future – or not. :) It is most definitely arbitrary, which makes it even more fun to discuss.


    “… and a happy new year!”

  102. Buzz Parsec

    Oh yeah, and Happy New [insert arbitrary unit of time here], everyone!

  103. wildride

    This year is the end of “a” decade, specifically the one that started 10 years ago at the beginning of year 2000. But 2010 is the beginning of the last year of “the” decade as in ((current year minus first year) modulus 10)==9). If it equaled 0, then it would be a new decade, and so will be in 2011. That’s just a fact and no amount of whining will change it. Determine for yourself which you deem important, but just be aware of the difference.

    The fact is, they’re all pretty arbitrary, but the math is correct for one and incorrect for another.

  104. Perhaps this needs a little clarification.

    If I collected bricks and stacked them in piles of ten, nobody in their right mind would argue that the first brick in each stack was NOT the first brick of the stack.

    Years are different, because they have been around for as long as the Earth has been orbiting the Sun. We only see a significant issue of definitions because we have a story about some guy who was supposed to be born in a certain year, which we’ve chosen to call “1”.

    Moving the concept of the year back over to the brick analogy… well, it’s like suddenly waking up to find yourself stacking bricks in piles of ten, but being completely unable to remember ever starting, and the piles are stretching off behind you beyond the horizon – and then somebody comes along and says, “actually, the REAL bricks began at this point here, just above the first brick in that pile about 200 stacks ago, which means that there are only NINE bricks in that pile, and therefore you’re stacking them wrong because I SAY SO.

    Me? I’d laugh at that person, and carry on stacking my bricks and calling the bottom one the first brick…

  105. Huron


    Your bricks are gonna come crashing down. The analogy is horribly, horribly flawed. Need I quote the Royal Observatory at Greenwich again? This is an astronomy blog. They get the last word.

  106. foole

    martin_mullv(“We used to have a bus.”); /* Martin Mull on The Simpsons */
    george_carlinv(“In a way The Sixties ended the day we sold it. December 31st, 1969.”); /* George Carlin on The Simpsons */

  107. sapphie

    Phil, doesn’t this sound just a bit arbitrary? I mean sure, it sounds elegant the way you put it, especially noting how awkward it would sound if we counted decades from Year One. Yet your qualification is simply that “we” do it a particular way. Who is this “we” you keep mentioning? Can you cite a more authoritative source for your claim than some nebulous “we”? Until I see something better than that, I’m not buying your argument, sorry.

  108. Petrolonfire

    @60. Strangel Says:

    Well, I say we’re not going to Jupiter so who cares what year or decade it is?

    Well *I* say we *are* going to Jupiter so there! 😉 😛

    In fact, we’ve already been to Jupiter a number of times – Pioneer 11, Pioneer 10, Voyager 1, Voyager 2, Galileo, New Horizons … :-)

    If you mean sending humans to Jupiter rather than just robots, well that may happen too one day. And although we’ll never walk _on_ Jupiter since there’s no Jovian ground to walk on, we may get balloons into the Jovian upper atmosphere which, sorta, counts .. doesn’t it? 😉

    I look at it this way, there’s technically pedantically correct dates for the decades end & then there’s what most people think and celebrate & it ain’t zero-sum. You can hold both in your mind and accept both as at least approximately valid.

    We can both argue intellectually over the precise technical moment of the decade and simultaneously we can go with the flow & say that by popular acclaimation (& TV news & FSM knows the TV is always right even when its wrong! 😉 ) the day that’s already over in some parts of the world (like where I live) is /was New Years Eve & today / tomorrow is New Years Day.

    Have a happy one everyone & may this be one of those decades where things go right for a change! 😀

  109. Plutonium being from Pluto

    @ 2. neutron Says:

    This 1st decade has been termed the “noughties” in the UK which I find quite amusing.

    Yeah, its also been tagged the ‘noughties’ here in Australia too – although there is some variation and discussion. I’m not sure that everyone is happy with it or has agreed on what to call the decade. Awkward really.

    @ 89. Eric TF Bat Says:

    And yes, that decade was the Noughties, and it ended last night. Now we’re into the Tenties. If you were naughty in the Noughties, will you be tense in the Tenties?

    Actually, I think we were naughtier in the 90’s and tenser in the ’00-ies. Here’s hoping this 21st century, which is about a tenth over, gets better and better – I do think I see some positive signs that this is happening.

    @ 99. Mike Torr Says:

    … In other words, the century began on 2000-01-01 (yes, I think the British and the Americans both have dates wrong. yyyy-mm-dd ftw!) …

    Yes. Year-month-day or day-month-year makes much more sense to me as you have things in order with scaled sequence. The Japanese use the year -month-day order which I prefer ie. today it’s 2 p.m. /1400 hrs, 2010 Jan. 1st where I live – Adelaide, South Australia if you’re curious.

    As for decades AND centuries, it’s totally arbitrary, as others have said. Nobody actually knows whether Jesus existed, and if he did we certainly can’t be sure when he was born. That being the case, surely we should use the simplest definition possible? Ockham’s Razor, you know? and the new decade begins on 2010-01-01.

    Yep. I agree. There are technical issues and arguments otherwise but I think the majority who go with the simple digits 9 -> 0 as the transition point will ignore the technicalities and since it really doesn’t matter, I’m going to go along with that – until next New Year’s Eve when I can use such pedantry for a bigger celebration again! 😉

    Anyhow, what year is it by the Muslim calander or the Jewish one or the Hindu or Chinese or … so forth.

    All this, to me, just shows that while we can precisely measure time it is still a very relative and subjective thing.

    Personally, I think we’d be well advised to change the “start counting point” from the birth of a religious figure whose existence, origins & exact birthdate are cloudy and not shared with everyone and wrong in terms of him being born in 4 BC anyhow. I suggest instaed of AD / BC or even its politically corrected BCE / CE version we begin all over again.

    Let’s start our centuries with an event which is well documented and which is shared by all humans whatever their faith and culture and which is really significent to Humanity – the first landing by people on another world – Apollo 11 touching down on the Sea of Tranquillity. Let’s make 1969 the year 0 or 1 depending on your taste and then this is year 40 /41 Post Moon Landing!

    Anyone with me here? 😀

    Oh & Happy New Year to the Bad Astronomer & all my fellow commenters & lurkers here. May you have clear skies and fun and safety all year & into the foreseeable future too! 😀

  110. JB of Brisbane

    @Chris #79 – when you count your fingers, which one is zero?
    What we are discussing here is the difference between counting numbers (which start at 1) and whole numbers (which start at zero). We are not measuring years like a number line, we are counting them from the (albeit arbitrary) first year. We do not actually finish the 201st decade of the Common Era (Anno Domini, if you prefer) until next New Year. But as for the so-called “Noughties”… yes, they’re over.
    Now, what to call this next bracket of years until the end of 2019 – the “Terrible Teens”, maybe?

  111. Mena

    Sorry but my brain runs on math and I just can’t wrap my head around a decade ending with a “9”. You have a case where only two conditions, AD or BC, exist so there is only one point where they meet. That we can call “0”. We use a number line that looks like this to describe what happened, as others have pointed out:
    What would have to have happened for the “this is the end of the decade” thing to work out is that this would have to exist:
    and then {-1, 0} and {0, 0, 1} would have to have occurred. That’s just painful to think about so I’m calling it a night. Happy New Year everyone!

  112. GalaxyGal

    Have a Happy New Year…..whatever decade it will be defined as.

  113. Ted Powell

    Given that time (at least in our universe) began 13.72 x 10^9 years ago, and that this number only has four significant figures, it really is a moot point whether the backward extension of any sequence of decades has a year or three missing at the far end.

  114. As has been pointed out, astronomical year numbering, and ISO-8601, have a year 0. This reckoning is no less valid than AD/BC. There really was no year 1 AD or BC, since AD counting was invented in the 6th century (i.e. the 500s) and not widely used until hundreds of years later, and BC not until about a thousand years later. AD and BC were originally applied to the Julian calendar, which was introduced before the year 1, by Julius Caesar, after whom it was named. The Romans typically counted from beginning of an emperor’s reign, or by who was consul that year. (And no, AUC was not used very much.) So nobody living in the year 1 AD or 1 BC ever knew it. 1 BC and 0 are equally valid ways to refer to the same year, so the decade 0-9 makes as much sense today as does referring to years 1-10 as “the first decade AD”, even if they didn’t to anyone two thousand years ago.

    I understand that in some East Asian countries, such as Korea, one is considered to be 1 year at birth, and therefore someone 20 years old, by our reckoning, would say that he or she was 21.

    Another thing to consider is numbering of days. We usually count them from 1, as well. But that was not how Romans counted days in the Julian calendar. They counted backwards to certain days of the month, like the famous ides of March. December 31 was called the day before the calends of January, December 30 was day 3 from the calends of January, etc. Pope Gregory also did the same in his calendar. Counting up from the beginning is more modern. And sometimes astronomers actually count day 0 of the month as synonymous with the last day of the previous month, e.g. 2009 Dec. 31 = 2010 Jan. 0.

  115. Seriously, why is it so hard to understand that AD1-9 (call that period “the singles”) wasn’t a decade but that 2000-2009 was? Is that really a difficult concept?

    It wasn’t the 201st decade of the common era by any means, of course, but it was a series of ten years, and that makes it both a decade and the (previous) decade.

    For what it’s worth, the 201st decade is still “the” decade, and now the 201xs (whatever the hell we’re calling them) is too.

    FWIW, it has nothing at all to do with the year 0 or its absence. 1 is still the first nonnegative year of AYN and ISO 8601.

  116. Here’s a different way of looking at it.

    Basically, what people don’t realize is that AD/BC calendar dating is really two overlapping dating systems (or timelines, or coordinate axes). Once that is recognized, all the BS disappears.

  117. Mike

    Damn straight, Phil.

  118. Tim G

    I think the 2010s should be referred to as the “oneties” (WON tees).

  119. jr565

    How are we defining the end of the century then or the end of the millenium? Would the 20th century end in 1999 or 2000 ? I would think that defining a centuries end would also determine how you would determine when the decade ended as well, otherwise you’d have the end of the decade in 1999 and then end of the century in 2000. And why the discrepancy?
    Our centuries begin with one and end with 0. Our millenium begin with 1 and end with 0. Our calendars don’t start at 0. There is no January 0 after December 31st.

  120. TravisM

    Thanks Phill… I’m turning 30 in about 2 weeks! HA!

  121. Phil, I enjoyed your amusing post, but let me offer a counter. Yours is based on the analogy to a person’s age — always confusing — and to the semantic definition of a decade. Here’s my article on the chronological argument: http://bit.ly/8aAH6k

  122. Kaleberg

    Are you sure the decade ends on 31 December? Does that account for the missing days when they shifted from Julian to Gregorian. Maybe the decade ends on 10 or 12 January? I’m not even going to get into the year thing.

  123. GeneralMusings

    I will give over and agree that it is the end of “A” decade ( depending upon what particular 10 year period you happen to be measuring). The end of “THE” decade will be December 31, 2010 by the currently accepted calendar.

    **stumbles off to find a bottle of aspirin and an ice bag**

  124. Thom

    Absolutely correct. They are all arbitrary demarcations anyway.

    I write the date every day (more or less). Every year, on January 1, I change one of the digits that I write. Every ten years, TWO of those digits change. It feels like the end of a minor era. I don’t care at all how many ten-year periods have elapsed since the arbitrarily chosen and generally accepted as incorrect birthdate of a person that may never have existed in the first place. I care that I am now writing “201x” instead of “200x.” It feels ever so slightly different.

  125. Harry Tuttle

    A Year Zero in historical time is absurd. Was the day after New Years 0/0/10? No, it was 1/1/10. Because there is no not-day of the no-month to measure.

    The best way to do this is measure elapsed years from a zero-point rather than current years from a zero point (our system) or elapsed years from a non-historical year-zero (like Buddhists do), but that adds two years (1 CE and 1 BCE are un-elapsed years) to our chronology. The astronomical system of a historical year zero is great for computation but a logical impossibility.

  126. Ryan

    It’s all arbitrary. A decade is simply a 10 year span. If you want to start counting at, say, the 1994 year, then a decade will have passed at the end of 2003. You’re all arguing over a calendar that is only recognized in parts of the world, which was arbitrarily divided by the supposed birth year of a supposed historical figure (and most biblical historians put Jesus’ birth somewhere between 6 and 4 BC, so it’s not even accurate by that account). The Jewish and Chinese calendars are completely different. So, what does that mean? It means that everyone is right. Or, perhaps more accurately, that no one is wrong. You want your decade to end on the zero year? Go ahead. You want it to end on the one year? Have a blast. You want it to end on the six year? Makes as much sense as the other 2 popular ways. It’ll become even more arbitrary, useless, even, when and if we start deep space exploration or colonizing other planets, because the planets will most likely have a longer or shorter solar orbit, not to mention axial rotation which would make the days longer or shorter.

  127. Brian Too

    My 2 cents.

    People talk about decades because they want some perspective on the world and their lives. It’s helpful to take stock of what happened, and what they’d like to happen in the future.

    It’s also relevant that people live approx. 100 years (ooh! I’m doing it already with the imprecision!). Therefore a group of 10 or so decades is a nice way of thinking about your life and your world.

    It is therefore a cultural and human perspective on time. Mathematical precision is not helpful and truly pedantic in this context. Decadal perspectives harken back to an agricultural past when what really mattered was when to plant, when to harvest.

    As many others have pointed out, since when have most people needed precision in order to make a party?

    And, since it’s a pleasant tradition, Happy New Year!


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar