In my country, 30-40 years back, people who needed a watch were those ones who travel regularly. And travel was mostly using public transport, trains and planes. Most or all of it operated using a 24h time. That button was very useful. Compare that to the mute/silence/DND physical button in iPhones today.

Also people who worked in confined spaces who wouldn’t know if it was day or night outside after a days job. My father who worked in an oil rig in Abu Dhabi used one. He gifted me one.

This was 1998.

Yes but why not just always use 24h time (or 12h if that’s what you like).

It’s a little strange that a dedicated button would be needed to switch between them, especially when the math to convert between them is so simple.

Exactly, my kids knew how to convert between the formats at a fairly young age.

OK, but who would use 12h time ? I never understood, this seems so backwards.

How about someone who was raised on 12h time and has used it for 70 years? Sure, the math to convert is pretty easy, but why?

Ok right. I didn't know people were used to that.

You didn’t know about 300 million Americans?

I doubt that anyone knows 300 million people let alone that many Americans.

I'd guess that the very large majority of people don't know that americans use 12h time, no. Why would they?

It is a bit strange, like being surprised some countries drive on the left side. xkcd 1053 of course, but people are still allowed to be surprised when someone went their entire life without picking up a fairly common factoid.

I am grappling with this but I can't.

You did not know that large parts of the world default to 12h time?

This is absolutely NOT an American thing. I am not American and have never lived there. I am 58 years old, British and Irish, and lived a decade in Nigeria and a decade in Czechia. I have travelled widely around Europe and can get by in 6 foreign languages.

12h time in real daily life is more common everywhere I have ever been. Only minor subsections of humanity -- military people, maybe -- work on the 24h clock.

In the operating room, all the wall clocks are 12 hours but all records kept by humans are 24 hour time.

I am 38 and British and use 24hr clocks exclusively. This is also very common on the continent - the French nearly always use 24hr time for everything

Thinking on, yes, I think I'd noticed that. I love the country but I've never lived there full-time, though.

Indeed (French here). 12h time is still there in spoken language sometimes, but never in writing.

I learnt English as a kid with the 12h time, but UK friends nowadays say they tend to use 24h everywhere precision is needed (e.g. transport timetables) and less and less 12h in everyday chat. I was supposing USA was the same. Obviously not.

> UK friends nowadays say they tend to use 24h everywhere precision is needed (e.g. transport timetables) and less and less 12h in everyday chat.

That is the direct opposite of my personal experience.

I do not live in the UK; I live in the Isle of Man, nearby. I visit for work often, though. Yes, the 24h clock is used for things like transport times, but in daily life, written and spoken, it is basically always 12h. I would estimate 95-99% of the time.

I.e. boomers holding everyone else back again.

People who can't reliably subtract 12 from numbers. They're out there.

It's me! (But I solve it by using 24h for everything)

Americans. The U.S. has a lot of people who are unaccustomed to 24 hour time.

It’s the whole Anglosphere. We do it, as well as imperial measurements, to give the finger to Napoleon and his metric 10 hour long day system.

But 24-hour time is not decimal, isn't it what you guys like?

It’s not the whole Anglosphere.

24 hour time is used extensively in the UK. For example, all public transport uses 24 hour times here.

I knew for the imperial units but not this. This country ... let's say it always amaze me.

They use US customary, not imperial, they're slightly different sets of units.

https://en.wikipedia.org/wiki/United_States_customary_units

> Some advocates of the customary system saw the French Revolutionary, or metric, system as atheistic. The president of an Ohio auxiliary of the Institute wrote that the traditional units were "a just weight and a just measure, which alone are acceptable to the Lord". His organization later went so far as to publish music for a song proclaiming "down with every 'metric' scheme".

Ooh that explains a lot.

How about just leaving it on 24h time all the time?

I just use 24h time in the afternoon.

Those buttons are the menu. The idea of menus on watches is a modern ux extravagance.

I don’t have the satisfying answer as to why they dedicated a button to 12/24 hour time but my guess is that it’s simply a cool digital feature and stands out against the limitations of analog watches.

They had modal menus back then, they just didn't display them. You had to memorize which obscure symbols to press, to change various settings. For example, in the 1970's, HP's calculator watch required pressing ⯅• to switch between 12 hr and 24 hr modes, or A⯅A to clear an alarm.

In the 80's and 90's, when sixteen-segment and dot-matrix displays made displaying text easier, calculators started displaying menu items, so you didn't have to memorize the sequence.

Since then, we've moved on to full-color high-resolution displays that can handle any text of any language, and the menus have more-or-less switched back to memorizing a sequence of which obscure symbols to press, I guess because some people think they look cool? Sometimes there's no menu at all, and you just have to memorize finger movements.

You can bury stuff like setting the time into a menu, people will accept it. They know that there will be a way to set the time. But if the 12/24 is hidden, whatever is picked as the default will drive away a noticeable fraction of those would-be buyers who prefer the other setting. For starters, pretty much everybody who does not get pulled into a sales person interaction that's sufficiently deep to touch the subject. And that sales person interaction won't be the best possibly, you don't want to bore them with nuisance settings, you want to show off The Stopwatch (or whatever was the flagship feature of the watch in question)

> required pressing ⯅•

I don't know what clever jiggery-pokery you are trying to do, but whatever you typed, it's just turning to tofu on this Macbook, in both Chrome and Firefox.

To add to it, I always kept the manuals around, because remembering the key press sequences was akin to doing combos in arcade fighting games.

A few months without doing them, and it was hopeless trying to remember how to do them again.

I always followed trial and error until I reached my target and I had the feeling that my results were much better than if I were randomly clicking buttons. That is, some memory always remained. Or the menu is well thought out and has some consistency.

The button press sequences are still combo-style; when I set one of the alarms on my ABL-100WE, it always ends in trial and error. I mean, basically it's logical, but when the buttons change what they do (e.g. when the display says "SET", the light button becomes "up"), it throws me off.

I have a 6.30AM alarm on my FW-91, and I'm too lazy to figure out how to switch it off.

15 beeps, btw, till it turns itself off for the day.

> 15 beeps, btw, till it turns itself off for the day

One thing I miss that’s not on my Fitbit is an hourly warning. When you have ADHD, it’s a huge helper.

> I'm too lazy to figure out how to switch it off.

Press MODE, then press ALARM ON/OFF.

Casio watches all have the same.

The beauty of them is that I can pick up any casio model from any year and I know how it works.

That my friend is peak design.

There are menus on these watches, though. On the F91w the menu button flips through different setting modes which affect the function of the other buttons.

I spoke with a Casio engineer about this. It's so that your bending wrist can accidentally switch it to 12h time when you actually really want it on 24h time or vice versa.

+1 I use this all the time and can't live without it

Is this a joke, or an actual answer?

They could just set it to 12h mode for americans and 24h mode for the rest of the world, and hid the setting somewhere deep in the menus (hold this button for 3s, then press that button 5 times, and then the other button two times, etc.), so you could change it from american to normal display if needed, and never again press it by accident.

My F-91F I replaced the Casio module with an Ollee watch and pretty much disabled all of the features, I can sync the time when reconnecting to Bluetooth on my phone which I do about once a month.

Newish Casio user here. From what I understand, it's so that you can switch it to 24h after accidentally switching it to 12h and vice versa.

Been using Casio watches since 1983. That is exactly what it is for.

HN makes me laugh like twice a year – you're either the first or second!

you mean the first or the thirteenth.

I see what you did there

Plus, you don't have to manually convert from 24h to 12h time.

The state of American math skillz.

To be fair I've been using 24h time all my life and I still sometimes say 5 when I meant 15 (3), at least once a year.

>euroderf

Name checks out.

You are joking, but perhaps it's exactly what it's for.

Well done!

casio guy here, can confirm thanks for the laugh

You are my hero for the day.

Wearing a Casio as I type this. The "24hr" button switches 12/24 modes on the "watch" mode, when using stopwatch it starts the watch, and when using alarms it turns the alarm on/off.

It has pretty critical functionality for those, I think the way its labeled on the watch face just makes it sound a little odd.

Now that I think I can't very fast come up with any feature I would want to have on third button in clock display mode. UI is 3 buttons, light, mode and one mode dependant. So I can't think what you would use it for in clock mode. So better have it work, but do something inconsequential...

Maybe it's because the United States is not the whole planet

A watch like the F-91W is a bit wonky in terms of the buttons. You're right the 24/12h makes no sense, who needs to switch between those two options regularly? The backlight button is also questionable, because it's not entirely clear what you're suppose to gain by vaguely illuminating the first 20% of display, which will be empty from midnight until 20:00.

At night it is more than sufficient. I even use it as a flashlight

And you specifically have an F91W? In pitch black, it maybe illuminates 2/3 of the screen for me. I can't imagine using it as a flashlight! But mine is newer, maybe the older ones have better lights.

Yes, F-91W still on its first battery. It's not a great flashlight, but it allows me to find back into bed and not run into anything

It has to be extremely dark though, or maybe mine has a worse than normal backlight. Other models are much better, it's just the F-91W.

The fact that Casio is well aware that the backlight is just terrible, but haven't fixed it in close to 40 years is hilarious and just makes me love it even more.

Oh yeah I have good blinds and live in an area with medium light pollution.

If you have so much ambient light… just look at the clock and read the numbers.

Even worse, my Casio can't even change the default mm-dd to my country's default dd-mm, keeps throwing me off.

I used to walk around with a Casio always, I would have welcomed this connectivity, but now I have a Pebble and I like the balance. Could have done without the HR monitor, and with GPS though (some features don't work without phone connection, too many I find). Other than that, perfect for me.

For me the 24h is buried... But then I can't change the default mm-dd to my country's default dd-mm, which just keeps throwing me off.

For a very long time, China and India used a mixture of the 12-hour and 24-hour formats, which meant they had to convert the time or switch between time formats multiple times par day. That was the intended use of this button.

Both countries have now officially switched to the 24-hour format.

I'm skeptical. Switching between time formats when you're used to it requires 0 cognitive effort, and certainly doesn't warrant a button. Eg in France, people use 24h time for display but talk in either 12h or 24h time depending on personal preference, so you might look at "17:00" and say "5" without even thinking about it, it's just a different name for 17.

True (and can confirm) but this assumes a lifetime's habit of interchanging the two.

It doesn't take long to learn to interchange. If you start today you won't be doing it tommorow, but if you keep it up in a few months you will. At least for the common times - you might have to think about what 10pm is if you normally go to bed before then.

It’s not quite the same when a schoolchild or a farmer has to figure out different train timetable formats depending on the railway company. It was the 1980s, and these were the first affordable watches available…

The SNCF doesn’t change its format when you travel to Brittany or Alsace.