# When did the 21st century begin? **URL:** \ **Category:** Factual Questions\ **Created:** [July 18, 2015, 8:16am UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495 "2015-07-18T08:16:28Z")\ **Posts on this page:** 10\ **Page:** 3
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [July 19, 2015, 9:12pm UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/41 "2015-07-19T21:12:07Z")
> [@Kiyoshi](#): > > Does the same rule apply to decades? For example, did the 80s technically begin on 1 January 1981? Nope. But the LAST year of the eighth decade of the 20th century began on January 1, 1980. ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [July 19, 2015, 9:17pm UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/42 "2015-07-19T21:17:20Z")
> [@Your\_Great\_Darsh\_Face](#): > > The first day of the month is day 1. The first month of the year is month 1. Why wouldn’t the first year of the century be year 1? > [@Aquadementia](#): > > Because there is no zeroth day of the month. There’s also no zeroth year of the century. And as far as I am concerned, there’s no such word as “zeroth.” Because it’s a stupid-sounding so-called “word,” that’s why. :dubious: ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [July 19, 2015, 9:19pm UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/43 "2015-07-19T21:19:54Z")
> [@Nema98](#): > > In a cultural sense 2000 was the beginning. I suspect 85 years from now people will ring in the new millennium at midnight Jan 1, 2100. Over my dead body! Probably. ---
**Author:** ![mr.jp](https://avatars.discourse-cdn.com/v4/letter/m/48db29/32.png) [@mr.jp](https://boards.straightdope.com/u/mr.jp)\ **Post date:** [July 19, 2015, 9:51pm UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/44 "2015-07-19T21:51:45Z")
I have thought a lot about this question, and here is how I think it is: We agree that the seventies are from 1970-1979. We also agree that the seventies were a decade. They were not the 198th decade after the birth of christ though. That was 1971-1980. But still the seventies have to be a decade. “The new century” (or millenium) therefore started at January 1st 2000 if you mean the century 2000-2099. However if you mean the 21st century after the birth of christ, that started at January 1st 2001. If people want to call the century that goes 2000-2099 the 21st century I don’t think that is incorrect. It isn’t the 21st century after the birth of christ, but it is the 21st century if you consider the centuries [-1 (or 0),99], [100,199],…,[2000,2099]. So the 21st century can be either the 21st element in the set of centuries that go [1,100],[101,200],…[2001,2100] or the 21st element in the set of centuries that go [-1,99], [100,199],…,[2000,2099] And I don’t think any of these two has a claim of being more correct than the other. It’s two different successions of centuries that each have their merit. I guess it would be nice if we could all stick to one of those successions, so we knew what each other were saying, but it doesn’t seem like that’s going to happen. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [July 19, 2015, 11:32pm UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/45 "2015-07-19T23:32:48Z")
[Cecil spoke about the ‘decade’ issue as well, though not as definitively.](http://www.straightdope.com/columns/read/1372/what-year-numbering-system-was-used-in-the-time-of-christ) Personally the whole thing is pretty simple to me: The ‘eighties’ are 1980 to 1989. The ‘eighth’ decade of the 20[sup]th[/sup] century was 1971 to 1980, but nobody ever refers to decades that way. I get that the 18[sup]th[/sup] century was 1701 to 1800, but I usually refer to past history with the more simple 1800s, 1700s etc. At least until you get earlier than 1000 CE, then saying the ‘800s’ doesn’t sound quite right compared to ‘the 9[sup]th[/sup] century’. Once you get into ‘negative’ dates, i.e. BCE, it becomes way too confusing to say anything but the actual date… 😃 ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [July 20, 2015, 12:44am UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/46 "2015-07-20T00:44:46Z")
2099 can’t get here soon enough. ---
**Author:** ![Your\_Great\_Darsh\_Face](https://avatars.discourse-cdn.com/v4/letter/y/ac8455/32.png) [@Your\_Great\_Darsh\_Face](https://boards.straightdope.com/u/Your_Great_Darsh_Face)\ **Post date:** [July 20, 2015, 7:46am UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/47 "2015-07-20T07:46:22Z")
> [@tomndebb](#): > > 2099 can’t get here soon enough. I’m prepared to wait. I doubt that there’ll be much of an upside to living to 139 even if I somehow manage to make it that far. ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [July 21, 2015, 11:43am UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/48 "2015-07-21T11:43:00Z")
> [@tomndebb](#): > > [The Master speaks.](http://www.straightdope.com/columns/read/120/the-millennium-approacheth-will-it-start-jan-1-2000-or-jan-1-2001) Here, Cecil says, > [@](#): > > In 24-hour time systems, in which the last minute of the day begins at 2359, there is no real need for terms like noon, midnight, AM, or PM. Astronomers use such a system with noon as the beginning of the day, or 0000; in the more familiar military system, noon is 1200. Noon for me is 1200, but for astronomers is 0000? Far be it from me to question Cecil, but, really? ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [July 21, 2015, 11:56am UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/49 "2015-07-21T11:56:30Z")
> [@Bullitt](#): > > Here, Cecil says, > Noon for me is 1200, but for astronomers is 0000? Far be it from me to question Cecil, but, really? Sure. Astronomers don’t want to change the date on their observations half-way through their lunch break (what diurnal people would call a “midnight snack”). ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [July 21, 2015, 12:15pm UTC](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495/50 "2015-07-21T12:15:32Z")
That makes sense, thanks. [Previous page](https://boards.straightdope.com/t/when-did-the-21st-century-begin/725495.md?page=2)