It's not confusing for us Europeans since we use 24 hour clocks. Midnight is 00. However I did not understand the reason the 24 hour clock caught on until now. TV schedules use 24 hour clocks to avoid this ambiguity.
Why is 11 am and 1 hour == 12:00 pm?
41–50 of 67 posts
Re: Why is 11 am and 1 hour == 12:00 pm?
#42I don't want to be offensive, but this is just another example where anglo-american standards for time and length measurements are ill-defined and lead to confusion. Instead, we have the SI system for the rest of the world and we have international standards for counting time -- with time going from 00:00:00 to 24:59:59 a day. I wonder why people refrain to adopt a working system in favour of culture. I never underst…
The biggest difficulty for people will be forming new habits. The military time convention is familiar but cumbersome. Saying "I'll see you at 17 hundred hours" is not as convenient as "I'll see you at 17 o'clock" or simply "I'll see you at 17". The latter two sound a bit weird (especially the last one), but they're perfectly natural in other languages so it's just a matter of figuring out how to overcome the initial unfamiliarity in a large part of the population. I for one think this would be a great thing to standardise on just like SI.
Re: Why is 11 am and 1 hour == 12:00 pm?
#43Earlier quoted context omitted.
> anglo-american Do Spanish-American (and others) use kilos, metres, Celsius and all the rest? I'd assumed not, since the Quebecers I know use American measurements for their body and cooking. But I'd like to be wrong. (You could also have meant anglophone, but that's too broad. 23:05 is fully understood in Britain, and the normal way to write the time on timetables and so on.)
Wikipedia: "As of 2017, seven countries formally do not use the metric system as their main standard of measurement: the United States, Myanmar, Liberia,[3] Palau, Marshall Islands, the Federated States of Micronesia, and Samoa.[4] However, both Myanmar and Liberia are reportedly essentially metric, even without official legislation." https://en.wikipedia.org/wiki/Metrication
Formal use is different that widespread consistent use, excluding the other system.
My observation, at least where I live, is that both systems are used in practice. Especially at grocery stores, where the aim seems to be intentional confusion. For example you buy oranges listed for 2.34 a pound, but at the register you are charged 5.74 a kilo. Where you charged the correct rate? Maybe? Maybe not?
Re: Why is 11 am and 1 hour == 12:00 pm?
#44The instant it becomes noon, it is no longer ante meridian (before noon). Thus we have to make an arbitrary allocation, and it makes a lot more sense to lump 12:00 with 12:01-12:59, rather than with 11:00-11:59.
Re: Why is 11 am and 1 hour == 12:00 pm?
#45[deleted]
Re: Why is 11 am and 1 hour == 12:00 pm?
#46You’ll probably never see a flight or a movie or something start right at 12:00; it’s just so much clearer at a glance to see that 11:55 AM/PM.
A while back I wrote a calendaring application where I encountered a similar problem and came up with a similar solution. If someone scheduled an all day meeting that ended at 12 midnight, the calendar would show it as a two-day meeting. The meeting started at 12AM on January 8th and ended at midnight of the same day... but since January 8th ends at 11:59PM and January 9th begins one minute later, the invite would roll over and be displayed as ending the next day. I'm not actually a real programmer (I just pretend to be one when someone wants to pay me) so this took way longer to figure out than it really should have.
I tried various things like if a meeting says 12AM, subtract one day, but then I'd encounter edge cases like meetings that start at 12AM now showing the previous day, or meetings that are scheduled from 12AM on the 8th to 12AM on the 8th (basically zero-minute durations) showing the wrong day or a bunch more things you don't think of until you try to develop applications for end users you might never talk to.
Eventually I set it to make any meeting that ended at 12AM just subtract one minute from the overall duration so it would end at 11:59PM instead. It didn't as much solve the problem as it did just avoid it, but at least people stopped complaining.
Re: Why is 11 am and 1 hour == 12:00 pm?
#47You’ll probably never see a flight or a movie or something start right at 12:00; it’s just so much clearer at a glance to see that 11:55 AM/PM.
Only trains to Georgia
Re: Why is 11 am and 1 hour == 12:00 pm?
#48This has always been a pet peeve of mine. Makes it really hard to answer simple questions like, how many hours pass between 11am and 12am?
Re: Why is 11 am and 1 hour == 12:00 pm?
#49I thought continuity provides an answer: 11:59:59.9999999999 is still AM. 12:00:00.0000000001 is clearly PM. When should the AM switch to PM? My intuition says at the same time that the 11 switches to a 12 (and all the 9's switch to 0's). Thus, noon is pm. Having said that, in reality the solution is banish the abominable 12 hour clock, and use the 24 hour clock. That also removes the ambiguity whether "Midnight on J…
I believe the actual answer is that there is no 12:00 AM or PM. You're meant to say "twelve noon" or "twelve midnight" rather than AM or PM for this exact reason. "actual answer" is maybe a bit strong - I read it somewhere but I can't remember where. The site or book or wherever it was that I read that did seem quite authoritative on the matter, however!
That's just a cop-out. If you change the question from 11 AM to 11:01 AM it's still just as valid, and there's no need to argue about the ambiguity. Is there anybody who would seriously argue that 12:00 AM plus one minute should be 12:01 PM? That way lies madness.
Re: Why is 11 am and 1 hour == 12:00 pm?
#50I thought continuity provides an answer: 11:59:59.9999999999 is still AM. 12:00:00.0000000001 is clearly PM. When should the AM switch to PM? My intuition says at the same time that the 11 switches to a 12 (and all the 9's switch to 0's). Thus, noon is pm. Having said that, in reality the solution is banish the abominable 12 hour clock, and use the 24 hour clock. That also removes the ambiguity whether "Midnight on J…
That's true for every hour though. The same argument applies to 10:59:59.99999 and 11:00:00
Pop quiz: How many hours passed between 11am and 12am?