# Year-numbering System **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [February 6, 2015, 12:34pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961 "2015-02-06T12:34:13Z")\ **Posts on this page:** 18\ **Page:** 2
**Author:** ![tim-n-va](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim-n-va/32/3001_2.png) [@tim-n-va](https://boards.straightdope.com/u/tim-n-va)\ **Post date:** [February 12, 2015, 6:07pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/21 "2015-02-12T18:07:47Z")
> [@Nadreck](#): > > It may seem a nitpicking distinction, but it isn’t. Claiming that the millenium ended at the end of 1999 is mathematically the same as claiming that the Indy 500 ends at the _beginning_ of the 200th lap, instead of at the end of it. The problem is that when you say “the millenium”, it has a specific meaning to you that is not universal. Some people think of the second millenium, some think of the millenium of years with a one in the thousands place. ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [February 12, 2015, 10:13pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/22 "2015-02-12T22:13:02Z")
> [@tim-n-va](#): > > The problem is that when you say “the millenium”, it has a specific meaning to you that is not universal. Some people think of the second millenium, some think of the millenium of years with a one in the thousands place. No good. “The _n_th millennium” (or “the millennium” clearly elliptical for “the _n_th millennium”) is not the same thing as bare “the millennium”. ---
**Author:** ![tim-n-va](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim-n-va/32/3001_2.png) [@tim-n-va](https://boards.straightdope.com/u/tim-n-va)\ **Post date:** [February 13, 2015, 12:12am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/23 "2015-02-13T00:12:12Z")
Can’t argue with that! ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [February 13, 2015, 4:52am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/24 "2015-02-13T04:52:55Z")
> [@Powers](#): > > Instead of just pooh-poohing accurate counting, perhaps you could share with us what is “lame-ass” about those assertions? > Powers &8^] Thank goodness the end of the century is over (Either end. Both Ends) And I don’t have to put up with lame-ass assertions. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [February 13, 2015, 6:20pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/25 "2015-02-13T18:20:37Z")
Instead, you just make them. ---
**Author:** ![jezzaOZ](https://avatars.discourse-cdn.com/v4/letter/j/a9a28c/32.png) [@jezzaOZ](https://boards.straightdope.com/u/jezzaOZ)\ **Post date:** [February 14, 2015, 12:41am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/26 "2015-02-14T00:41:55Z")
Cecil should note that Cambodia had a year zero when the the Khmer Rouge took over. ---
**Author:** ![Messy](https://avatars.discourse-cdn.com/v4/letter/m/5fc32e/32.png) [@Messy](https://boards.straightdope.com/u/Messy)\ **Post date:** [February 17, 2015, 6:34pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/27 "2015-02-17T18:34:40Z")
The whole thing is retroactive. ALL of it. In regular use, decades are used as a shorthand for eras or periods. For example, the Gay (as in happy) '90s refers to a specific cultural period in time which doesn’t necessarily add up to ten years. The “Fifties” for example, are generally agreed to have lasted from the Korean Armistice to the murder of JFK. The Sixties, are generally agreed to have lasted from then until Nixon’s resignation in 1974. The musical tastes of 1952 were generally the same as 1946, and '50s style rock was to some extent still going on in 1963. There was a sharp change music and art, and in 1965, it was culturally the ‘sixties’, so it was in 1971. I’ve heard lots of people call the early '70s “the '60s hangover.” The SEVENTIES was a short decade, you had Disco and Punk, and a cultural malaise that lasted until Reagan was in and the hostages out in January 1981. Decades tend to begin and end with a cultural BANG, like the one that blew off JFK’s head or knocked down the Berlin Wall. They may be close to ten year, or longer (the '90s lasted from '89 to 9/11) and we sort of can tell at the time when they’re going on, but defining them is retroactive. As to Centuries, It’s also retroactive. The first millennium AD wasn’t recognized as such until it was almost over. One AD is only RETROACTIVELY that, and the number zero wasn’t introduced to Europe until the 14th century (thank you Mr. Fibbinacci!). This does not mean that a retroactive year zero isn’t recognized anywhere. In the 17th century, Jacques Cassini, created an astronomical calender system which is used to this day (with modifications) which does indeed have a year zero. One AD is exactly the same as One CE (to use the PC CE/BCE system), but One BC is Zero CE and Two BC is One BCE. In other words, the 21st Century AD began in 2001 while the 21st century CE began in 2000. I hope this helps. ---
**Author:** ![Verily](https://avatars.discourse-cdn.com/v4/letter/v/e9a140/32.png) [@Verily](https://boards.straightdope.com/u/Verily)\ **Post date:** [February 17, 2015, 8:09pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/28 "2015-02-17T20:09:33Z")
> [@Messy](#): > > The whole thing is retroactive. ALL of it. In regular use, decades are used as a shorthand for eras or periods. For example, the Gay (as in happy) '90s refers to a specific cultural period in time which doesn’t necessarily add up to ten years. > > The “Fifties” for example, are generally agreed to have lasted from the Korean Armistice to the murder of JFK. The Sixties, are generally agreed to have lasted from then until Nixon’s resignation in 1974. The musical tastes of 1952 were generally the same as 1946, and '50s style rock was to some extent still going on in 1963. There was a sharp change music and art, and in 1965, it was culturally the ‘sixties’, so it was in 1971. I’ve heard lots of people call the early '70s “the '60s hangover.” The SEVENTIES was a short decade, you had Disco and Punk, and a cultural malaise that lasted until Reagan was in and the hostages out in January 1981. Decades tend to begin and end with a cultural BANG, like the one that blew off JFK’s head or knocked down the Berlin Wall. They may be close to ten year, or longer (the '90s lasted from '89 to 9/11) and we sort of can tell at the time when they’re going on, but defining them is retroactive. > > As to Centuries, It’s also retroactive. The first millennium AD wasn’t recognized as such until it was almost over. One AD is only RETROACTIVELY that, and the number zero wasn’t introduced to Europe until the 14th century (thank you Mr. Fibbinacci!). This does not mean that a retroactive year zero isn’t recognized anywhere. In the 17th century, Jacques Cassini, created an astronomical calender system which is used to this day (with modifications) which does indeed have a year zero. One AD is exactly the same as One CE (to use the PC CE/BCE system), but One BC is Zero CE and Two BC is One BCE. In other words, the 21st Century AD began in 2001 while the 21st century CE began in 2000. > > I hope this helps. I don’t think if “helps” because there aren’t a lot of facts in here. A lot of opinion based on cultural changes and historical events, but there’s not much there that has anything to do with why decades are named after which years they contain. A case can be made that 1971 was effectively still the '60s in a cultural sense. But that’s not what the phrase “the 1960s” means in a literal sense. The problem is that Cecil is thinking of decades as being counted in the same way that centuries are, when clearly they are not. The centuries are counted the way they are because they are counting the number of centuries elapsed from the (as it turns out) arbitrary starting point that our calendar uses. And because our calendar was created by someone who lacked a concept of “0”, there was no year 0. Therefore the first century of the new calendar started with the year 1. So to be a full century, the first century has to be counted as spanning from year 1 to year 100. The second century then starts with 101 and ends with 200, and so on. So the twentieth century started at 1901 and ended with 2000, and the twenty-first century started at 2001 and will end with 2100. Decades don’t work that way because we’re not counting the number of decades from year 1, or even year 1901. When we refer to a decade, we’re just saying “this particular span of ten years.” And when we refer to a decade as “the '60s”, we’re talking about those ten years that have a 6 in the 10s place. We’re not saying it’s the sixtieth decade since a given year, or even the sixth. The 1960s are just “the years that are all nineteen-sixty-something.” Hence, “the '60s” are “1960 through 1969”. And regardless of how much Cecil may have wanted 1990 to be part of the '80s, and regardless of how cultural commentators may observe that the music of 1990 sounded more like the music of 1985 than of 1995, the 1980s ended on December 31st, 1989, followed promptly by the 1990s on January 1st, 1990. The way we count centuries and the way we designate (NOT “count”) decades are apples to oranges. ---
**Author:** ![Powers](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Powers](https://boards.straightdope.com/u/Powers)\ **Post date:** [February 18, 2015, 2:27am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/29 "2015-02-18T02:27:29Z")
> [@Messy](#): > > One AD is exactly the same as One CE (to use the PC CE/BCE system), but One BC is Zero CE and Two BC is One BCE. In other words, the 21st Century AD began in 2001 while the 21st century CE began in 2000. Completely and totally wrong. “Common Era” is a synonym for “Anno Domini”, and “Before the Common Era” a synonym for “Before Christ”. They are completely interchangeable. Powers &8^] ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [February 18, 2015, 4:37am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/30 "2015-02-18T04:37:46Z")
> [@Powers](#): > > Completely and totally wrong. “Common Era” is a synonym for “Anno Domini”, and “Before the Common Era” a synonym for “Before Christ”. They are completely interchangeable. > Powers &8^] This myth seems to be spreading, though. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [February 18, 2015, 7:09am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/31 "2015-02-18T07:09:50Z")
He seems to be talking about [astronomical year numbering](http://en.wikipedia.org/wiki/Astronomical_year_numbering). > [@](#): > > Astronomical year numbering is based on AD/CE year numbering, but follows normal decimal integer numbering more strictly. Thus, it has a year 0, the years before that are designated with negative numbers and the years after that are designated with positive numbers.[1] > [@](#): > > Finally, in 1740 the French astronomer Jacques Cassini (Cassini II), who is traditionally credited with the invention of year zero,[7][8][9] completed the transition in his Tables astronomiques, simply labeling this year 0, which he placed at the end of Julian years labeled avant Jesus-Christ (before Jesus Christ or BC), and immediately before Julian years labeled après Jesus-Christ (after Jesus Christ or AD).[2] > > Cassini gave the following reasons for using a year 0:[10] > > _The year 0 is that in which one supposes that Jesus Christ was born, which several chronologists mark 1 before the birth of Jesus Christ and which we marked 0, so that the sum of the years before and after Jesus Christ gives the interval which is between these years, and where numbers divisible by 4 mark the leap years as so many before or after Jesus Christ._ > —Jacques Cassini > > [snip] > > Jean Meeus gives the following explanation:[11] > > _There is a disagreement between astronomers and historians about how to count the years preceding year 1. In [Astronomical Algorithms], the ‘B.C.’ years are counted astronomically. Thus, the year before the year +1 is the year zero, and the year preceding the latter is the year −1. The year which historians call 585 B.C. is actually the year −584. The astronomical counting of the negative years is the only one suitable for arithmetical purpose. For example, in the historical practice of counting, the rule of divisibility by 4 revealing Julian leap-years no longer exists; these years are, indeed, 1, 5, 9, 13, … B.C. In the astronomical sequence, however, these leap-years are called 0, −4, −8, −12, …, and the rule of divisibility by 4 subsists._ > —Jean Meeus Also this [NASA page](http://eclipse.gsfc.nasa.gov/SEhelp/dates.html): > [@](#): > > However, Exiguus’ dating system still lacks a “0” year which makes calendrical calculations awkward. The “astronomical” dating system refers to an alternative method of numbering years. It includes the year “0” and eliminates the need for any prefixes or suffixes by attributing the arithmetic sign to the date. Thus, the astronomical date for 2000 CE is simply +2000 or 2000. The astronomical year 0 corresponds to the year 1 BCE, while the astronomical year -1 corresponds to 2 BCE. In general, any given year “x BCE” becomes “-(x-1)” in the astronomical year numbering system. Historians should take care to note the numerical difference of one year between “BCE” dates and astronomical dates. Astronomers, however, don’t use BCE vs CE, they use negative years CE. It’s a conflation of two issues, the CE/BCE vs AD/BC convention and the astronomical convention to add a year 0. ---
**Author:** ![Messy](https://avatars.discourse-cdn.com/v4/letter/m/5fc32e/32.png) [@Messy](https://boards.straightdope.com/u/Messy)\ **Post date:** [February 19, 2015, 5:45pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/32 "2015-02-19T17:45:36Z")
Just be glad we don’t use the metric system or it would be 1 Ventôse CCXXIII. The reason we all use the Gregorian/Dionysian calender is because we have always used it. Also, they use the retroactive year zero in European textbooks. I know this because I have some. I also have noticed that there really were very few references to a decade having a nickname until the 1890s. ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [February 20, 2015, 1:44am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/33 "2015-02-20T01:44:09Z")
The French Revolutionary Calendar lasted only 12 years, and has no direct connection with the Metric System, which was already a work in progress before the Revolution. The Dionysian era, is quite old, but hardly “always”. The Gregorian Calendar is only a few centuries old. Moreover, it has actually _never_ been used in English-speaking countries. England, not wishing to co-operate with the RC Church in any way, lest it get Pope Cooties, devised an entirely new calendar called “New Style”, which gives the same results as the Gregorian Calendar by an _amazing coincidence_. Yup, an amazing coincidence, that’s it. (The more revolutionary parts of Eastern Christianity have a third calendar, called “Reformed Julian”.) I’d want to see these “textbooks” of yours. A year A.D.zero equal to 1B.C. may, of course, be introduced to simplify certain calculations, but I am unaware of any western historian using it, and I doubt very much that textbooks putting the assassination of Gaius Julius Caesar in 43B.C. would be likely to sell very many copies. (Astronomers calling it “-43A.D.”, as has been explained, is another matter. Astronomers also put the transition between one day and another at noon.) ---
**Author:** ![florencetaylor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/florencetaylor/32/7318_2.png) [@florencetaylor](https://boards.straightdope.com/u/florencetaylor)\ **Post date:** [February 24, 2015, 6:21am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/34 "2015-02-24T06:21:17Z")
Yes, but FORTRAN was designed to do it the way mathematicians do, while C was designed to do it the way computers do. And you’re gonna get fencepost problems either way. I wonder what Plankalkül did. The 8th decade of the 20th century was from 1971 to 1980. The 80s were from 1980 to 1989. ---
**Author:** ![JimSC](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@JimSC](https://boards.straightdope.com/u/JimSC)\ **Post date:** [February 24, 2015, 9:33pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/35 "2015-02-24T21:33:42Z")
> [@Irishman](#): > > Also this [NASA page](http://eclipse.gsfc.nasa.gov/SEhelp/dates.html): > > Quote: > However, Exiguus’ dating system still lacks a “0” year which makes calendrical calculations awkward. The “astronomical” dating system refers to an alternative method of numbering years. It includes the year “0” and eliminates the need for any prefixes or suffixes by attributing the arithmetic sign to the date. Thus, the astronomical date for 2000 CE is simply +2000 or 2000. The astronomical year 0 corresponds to the year 1 BCE, while the astronomical year -1 corresponds to 2 BCE. In general, any given year “x BCE” becomes “-(x-1)” in the astronomical year numbering system. Historians should take care to note the numerical difference of one year between “BCE” dates and astronomical dates. If we designate the interval before Year 1 as Year 0, then the interval before Year 0 should be Year -0. Think about the age of a child. 12 months after birth the child is one year old. We consider the child to be one year old throughout the 2nd year of life. (Even though we don’t think about it this way,) a six-month-old is zero years old. To project this accounting in reverse, six months prior to the birth would have to be in Year -0, and 18 months prior to birth would be in Year -1. In effect, this system doesn’t have an origin at Point 0, it has an origin at Point X centered in a two year period from -1 to +1. The discrepancy in the current calendar results from considering Year 1 to begin at t = 0 and end at t = 1 yr, when we consider a child to be one year old between t = 1 yr and t = 2yrs. ---
**Author:** ![Messy](https://avatars.discourse-cdn.com/v4/letter/m/5fc32e/32.png) [@Messy](https://boards.straightdope.com/u/Messy)\ **Post date:** [February 25, 2015, 9:22pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/36 "2015-02-25T21:22:58Z")
. > [@](#): > > The French Revolutionary Calendar lasted only 12 years, and has no direct connection with the Metric System, which was already a work in progress before the Revolution… The Metric System was NOT in use prior to the French revolution. It was extablished with the Calender and religion (the two parts of it that failed.) and the rest were legislated in The French law of 18 Germinal, Year III (7 April 1795) and completely adopted in 1799 (our time). ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [February 25, 2015, 11:00pm UTC](https://boards.straightdope.com/t/year-numbering-system/711961/37 "2015-02-25T23:00:23Z")
> [@Senegoid](#): > > The calendar was presumably designed by FORTRAN programmers. > > If it had been designed by C programmers, there would have been a Year 0. If it had been designed by [Sperry mainframe](http://en.wikipedia.org/wiki/UNIVAC_1100/2200_series) programmers, there would have been a Year [-0](http://en.wikipedia.org/wiki/Ones%27_complement#Negative_zero)! ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [February 26, 2015, 2:35am UTC](https://boards.straightdope.com/t/year-numbering-system/711961/38 "2015-02-26T02:35:34Z")
> [@Messy](#): > > . > > The Metric System was NOT in use prior to the French revolution. It was extablished with the Calender and religion (the two parts of it that failed.) and the rest were legislated in The French law of 18 Germinal, Year III (7 April 1795) and completely adopted in 1799 (our time). I did not say it was in use prior to the Revolution, I said it was a work in progress. The initial authorization for the project was signed by Louis XVI. [Previous page](https://boards.straightdope.com/t/year-numbering-system/711961.md?page=1)