# Decades, Centuries, Millenia...? **URL:** \ **Category:** Factual Questions\ **Created:** [March 7, 2004, 10:26pm UTC](https://boards.straightdope.com/t/decades-centuries-millenia/233026 "2004-03-07T22:26:59Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![The\_Immortal\_Mango](https://avatars.discourse-cdn.com/v4/letter/t/da6949/32.png) [@The\_Immortal\_Mango](https://boards.straightdope.com/u/The_Immortal_Mango)\ **Post date:** [March 7, 2004, 10:26pm UTC](https://boards.straightdope.com/t/decades-centuries-millenia/233026/1 "2004-03-07T22:26:59Z")
What I want to know is what comes after millenia, what is the name for a million years? Also what comes after trillions? I know this isn’t life or death but its sort of being bugging me, I’d just like to know. So anyone out there who can shed light on this subject pleae lend a hand. If you can’t lend a hand but have a funny quip or remark then reply anyway, I could do with a laugh. ---
**Author:** ![Shade](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@Shade](https://boards.straightdope.com/u/Shade)\ **Post date:** [March 7, 2004, 10:55pm UTC](https://boards.straightdope.com/t/decades-centuries-millenia/233026/2 "2004-03-07T22:55:01Z")
If you google “kiloyear” or “megayear” you find some people using the standard SI prefixes with ‘year’. Not very standard though. But I doubt you’ll do better. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [March 7, 2004, 10:58pm UTC](https://boards.straightdope.com/t/decades-centuries-millenia/233026/3 "2004-03-07T22:58:38Z")
The term _eon_ is sometimes used in the generic sense to refer to a period of one billion years. The term is also used as a geologic time unit which may vary from hundreds of millions to billions of years. Other time units include: _era, period, epoch, and age_. Cite and more info may be found here: [http://www.palaeos.com/Timescale/timeunits.html](http://www.palaeos.com/Timescale/timeunits.html) You can also do a web search on “Geological Time Scale.” ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [March 7, 2004, 11:07pm UTC](https://boards.straightdope.com/t/decades-centuries-millenia/233026/4 "2004-03-07T23:07:44Z")
> [@The\_Immortal\_Mango](#): > > …Also what comes after trillions? You realize that you jumped right from “millions” to “trillions,” and want to know what comes after that, right? What about billions? 🙂 Anyway, trillions of years and beyond is kind of a non-issue, as the universe is only [13.7 billion years old](http://map.gsfc.nasa.gov/m_mm/mr_age.html). A trillion years is equivalent to 1,000 billion years. We’ve got a ways to go before we have to worry about time scales in the trillions of years. (If you really have to know what comes after a trillion, see the SDMB mailbag article [here](http://www.straightdope.com/mailbag/mgazilli.html).) ---
**Author:** ![Bytegeist](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@Bytegeist](https://boards.straightdope.com/u/Bytegeist)\ **Post date:** [March 7, 2004, 11:13pm UTC](https://boards.straightdope.com/t/decades-centuries-millenia/233026/5 "2004-03-07T23:13:07Z")
> [@The\_Immortal\_Mango](#): > > What I want to know is what comes after millenia, what is the name for a million years? Also what comes after trillions? I know this isn’t life or death but its sort of being bugging me, I’d just like to know. So anyone out there who can shed light on this subject pleae lend a hand. If you can’t lend a hand but have a funny quip or remark then reply anyway, I could do with a laugh. As **robby** says, a _billion_ years (10[sup]9[/sup]) is sometimes called an _eon_ by geologists. But of course, _eon_ also has the more vague meaning of just “a really really long time”. There’s not much call for naming a trillion year period, since the universe is only about 14 billion years old. I suppose you might be looking ahead to the future though. Got your eye maybe on a trillion-year mortgage? Otherwise, I’d suggest _mega-_, _giga-_ and _tera-year_. However rarely they might be used, they’re as good a choice as anything else. ---
**Author:** ![Shade](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@Shade](https://boards.straightdope.com/u/Shade)\ **Post date:** [March 7, 2004, 11:24pm UTC](https://boards.straightdope.com/t/decades-centuries-millenia/233026/6 "2004-03-07T23:24:57Z")
> [@](#): > > There’s not much call for naming a trillion year period, since the universe is only about 14 billion years old. I expect we’ve spent longer discussing it’s name than anyone has spent using it 😃 It might crop up in extrapolations… ‘heat death in…’ Otherwise, it’ll become relevant in about 985,000,000,000 years. So if this thread re-occurred once a year until then, and takes 1 minute to type, we would _waste as long as the human race has currently existed typing out this question repeatedly_. I recognise the irony is taking the time to make this calculation (I just thought it was funny for some reason.) ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [March 7, 2004, 11:26pm UTC](https://boards.straightdope.com/t/decades-centuries-millenia/233026/7 "2004-03-07T23:26:05Z")
What comes after billions? The budget deficit.