# "Natural" basis for the hour?

**URL:** https://boards.straightdope.com/t/natural-basis-for-the-hour/529700
**Category:** Factual Questions
**Created:** [February 19, 2010, 10:11pm UTC](https://boards.straightdope.com/t/natural-basis-for-the-hour/529700 "2010-02-19T22:11:02Z")
**Posts on this page:** 3
**Page:** 2

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### Author: ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)
#### Post date: [February 25, 2010, 12:13pm UTC](https://boards.straightdope.com/t/natural-basis-for-the-hour/529700/21 "2010-02-25T12:13:31Z")

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Os, so that explains it for this side of the world. What about Ancient Asia or Pre-Columbian America? Were they base 12 too? Something else?

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### Author: ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)
#### Post date: [February 25, 2010, 12:22pm UTC](https://boards.straightdope.com/t/natural-basis-for-the-hour/529700/22 "2010-02-25T12:22:00Z")

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> [@njtt](#):
>
> I believe the Romans divided the day (i.e., from sunrise to sunset) into 12 hours, but the night into four _watches_. Thus a summer hour was longer than a winter one (and a summer _watch_ correspondingly shorter).

I’m struggling to see how this worked. Unless you knew when the sun was going to rise and set, how would you know how long to make each hour/“watch”?

And if you _did_ know when the sun was going to set, you’d still have to use a constant-length measure of time to fix that and so work out how long each hour was going to be.

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### Author: ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [February 26, 2010, 2:18pm UTC](https://boards.straightdope.com/t/natural-basis-for-the-hour/529700/23 "2010-02-26T14:18:11Z")

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> [@Colophon](#):
>
> I’m struggling to see how this worked. Unless you knew when the sun was going to rise and set, how would you know how long to make each hour/“watch”?
> 
> And if you _did_ know when the sun was going to set, you’d still have to use a constant-length measure of time to fix that and so work out how long each hour was going to be.

This is merely an educated guess but:  
[ul]  
[li]They knew when the sun was going to rise and set.[/li][li]The constant-length measure of time was called “a day”.[/li][li]When your main time keeping device is a sun dial, setting this up isn’t that hard.[/li][/ul]

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