Hey everyone…
I’m trying to create a unified format for specifying times in my app…
I feel inclined to use the 24 hour format, so that 10:15 in the evening is 22:15.
I have some questions for you depending on where you live:
Do people in America/Canada relate to the 22:15 format?
Do people in continental Europe relate to the 10:15pm format?
Can you suggest a format that is universally related to?
Be interesting to hear your answers!
Best wishes,
Antony.
Tempted to suggest Minkowski space-time is a close to universal as you will get 
Personally I would use a 12/24 hour toggle to avoid the issue. USA tends to be pretty settled on 12 so picking that as a default as Europeans are usually ok with that.
Americans casually refer to the 24 hour clock as “military time”. And I fear if you used a 24 hour format here, you’d have a non-trivial % of users thinking “17 O’clock? How can it be 17 O’clock???”.
Early on in my career, we had an app that used 24 hour clock. The amount of bug reports we got from users saying, “The clock is broken” was surprisingly high and caused me to question the future of our species. Maybe not quite that dramatic, but it was frustrating.
Didn’t end up mattering, our company got bought and shut down anyway 
I always use 24 hours in my daily life. But ya the future of our species is hanging in the balance 
I can’t speak for Canada, but as others have noted, most Americans definitely relate better to the 12-hour AM/PM format (unless you’re targeting veterans or other military personnel as @edd mentioned).
Morning, afternoon, evening, and bedtime. 
50% of Americans - “What the hell is 22:15?”
30% of Americans - “I know this, I knooooow this… damn. Hey Siri!”
American Military - “Idiots!”
Yes, I’m an American. No, won’t say which of those I fit in 
I’m American, but have lived overseas for 8 years…I still find myself having to ask myself “What is 22:15 minus 12? Oh yeah, thats 10:15PM”
What’s even spookier is that that 80% are allowed to vote. 
I can answer as a Canadian in Toronto. We always use AM and PM for pretty much everything from meeting invites, calendar invites, the time on our phones, to making plans and so on. However if you were to show someone a time and have 17:30 no one would be like “what is that!?!?!?!” but would probably bust out the fingers being like 13, 14, 15, 16, ah that’s 5:30pm! The only time I could see a Canadian disliking having to use 24 hour time would be if it’s maybe something they are using constantly. For example if I forced all my employee’s calendar to only work in 24 hours, I’d be hearing it pretty quickly from them how it takes too long trying to figure out what time is what. But if it’s something where you’re booking a doctor’s appointment, or receiving a confirmation on a service call at your home and it shows the time in 24 hours, no one would ever complain by that or be confused by what it means.
The default setting on anything here is going to be 12 hour time with AM and PM, so anyone that is using 24 hour time would have specifically gone in and picked that. I’m scratching my head trying to think of something I use that shows 24 hour time but nothing comes to mind. Often times in programming you’ll see in the logs it will be in 24 hour time which I much prefer as then there’s no confusion, but you would never have a friend or colleague text or email you saying “Are you free at 15:30 today?” It would ALWAYS be “Are you free at 3:30 today?” The AM/PM is generally skipped as well as usually it’s obvious or implied, since you of course most likely aren’t asking if they are free at 3:30 AM in the morning!
Hey everyone…
Thanks sooo much for your informative and witty replies!
All the best,
Antony.
