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Comment by arcticfox | Hacker News Reader

You're correct. We call the 24-hour clock "military time" and basically no one uses it casually.

I do. Granted, I was in the military-I passively hate it when people call it 'military time' (passively meaning I mentally roll my eyes when someone says it), but I've been using it since middle school when I first even learned it was a thing. Mostly because it made sense right away.

There are 24 hours in the day.

Why are we recycling numbers in our time system?

No really, why?

at a guess, its kinda the key size for hours

12/2=6, 12/3=4 work well, (with /4 and /6 being repeats of those)

24 hours doesn't add much on top of those divisions (you get /4 with a repeating /6 I guess)

I'm not immediately understanding, what are the divisions for? Parts/portions of the day?

Because there are only 12 major divisions on a clock. An analog clock, that is. It reads the same at 3am and 3pm. So from that pov it only makes sense to call it the same.

There are also analog clocks with 24 divisions.

https://en.wikipedia.org/wiki/24-hour_analog_dial

I guess 12 hour clocks are an easy trick to make them easier to read and manufacture and so on.

Sure, as a novelty. Who here has ever seen one like that in the wild? And yes, I think 24 is much harder to read, and not necessary either - in those situations where you don't know (when looking at a clock) whether it's 3am or 3pm, you have much bigger issues to worry about :)

My point was more in the second para, that 12 hour clocks aren't a platonic ideal, they are likely a result of practical demands. We make 12 hour dials rather than having them thrust upon us.

James Burke said in one of his shows that the 12 hour clock came in because it was ridiculous to have clock tower bells strike 24.

I was wondering what the rationale was.

Wouldn't they strike zero, for 00h00 since there's no 24h00 after 23h59.59? Which, admittedly, would be rediculous ;)

In the wild, not so much. But I have one in my home office---A nice one, purely mechanical (needs a key to wind it up). It's the second 24-hour clock I've had.

I love the idea of a 24 hour clock with 0000 at the bottom. Then the hour hand roughly follows the sun around all day, and a glance at the clock gives you the phase & time of day regardless of light cues or any other bits.

(Former submariner so a somewhat special case ;)

And the truth is that even when you live in a country where 24 hours notation is commonly used, like I do, you'll still more often say "5 in the afternoon", than 17 hours. The latter form is used in writing when you wish to sound more formal or when you really want to make sure there's no ambiguity. And not in the "army" style like 17 hundred, but you just say 17 or in written form 17h. All in all, it's just a matter of notation, once you're used to it sufficiently it translates to the clock face the same. Whether it's written as 13h or 1pm I visualise it exactly the same.

> Why are we recycling numbers in our time system?

Ever tried to read the clock on a sundial at night?

maybe it has something to do with sundials.

So that kids learn modular arithmetic ?

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