
Why is 11 am and 1 hour == 12:00 pm? - jsalinas
https://ell.stackexchange.com/questions/152603/why-is-11-am-1-hour-1200-pm
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FabHK
I 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 January 1st 2017" means
2017-01-01 00:00 or 2017-01-01 24:00 == 2017-01-02 00:00.

~~~
Finnucane
But whose 24 hour clock? Should we all be on GMT? That's arbitrary and
eurocentric. And let's get rid of those pesky arbitrary time zones too. We
should all be able to have our own personal time zones.

~~~
coldtea
> _But whose 24 hour clock? Should we all be on GMT? That 's arbitrary and
> eurocentric._

Doesn't matter. Anything would be arbitrary. Just pick one and be done with
it, and we already have GMT and UTC.

~~~
function_seven
Sorry if I misinterpreted your response, but do you think doing away with
timezones in "normal" life would be a net gain? I think it would add way more
confusion than it would eliminate. (e.g. "Let's have dinner Wednesday night"
would be very confusing in some parts of the world. "Is that the Wednesday
night just after Tuesday night? Or the one just before Thursday night?")

~~~
coldtea
> _Sorry if I misinterpreted your response, but do you think doing away with
> timezones in "normal" life would be a net gain? I think it would add way
> more confusion than it would eliminate._

It's the exact same information needed both today and after doing away with
timezones.

If you're in the same place as the other person, there's no confusion at all.
If everybody uses GMT, you know e.g. that diner around your parts (e.g.
London) is around 19:00 (7pm). If you live in California you know that diner
around your parts is around 03:00 (3am).

If you're in different countries, e.g. one is in London and the other is in
California, "Let's have a Skype at around 11:00" is unambiguous -- it will be
11:00 at both your clocks.

Lastly, if you're in different countries and you want to call someone in
California, and wonder whether now (11:00 GMT) is a good time, you just have
to know the offset number (the sun rises there 8 hours later) which is the
same as knowing the timezone.

Without timezones, it's only knowing the "part of the day" (whether it's late
or dusk or sunrise time etc) in another place that requires knowing an offset
(similar to knowing the timezone offset today).

All other calculations and coordination is vastly simplified.

> _(e.g. "Let's have dinner Wednesday night" would be very confusing in some
> parts of the world. "Is that the Wednesday night just after Tuesday night?
> Or the one just before Thursday night?")_

How is that confusing? Assuming we're talking about dinner, it would have to
be dinner time in the place those people live. So, e.g. a little before or
after sunset time on Wednesday. Whether that corresponds to 7pm or 2am or
12pm, people will know when it's that time where they live.

~~~
function_seven
What are we trying to solve by moving the world to UTC? We can't change when
the sun rises and sets, nor can we change our circadian rhythms. So what we're
left with is the fact that different parts of the world do things at different
times. Using timezones, we set the start, midpoint, and end of the day to
common numbers. If we ditch timezones and move to UTC-everywhere, we _still_
have timezones. They're just implicit now. And we also have the new burden of
our day changing while the sun is still up.

You waive off my dinner example as if "dinner" is a rigid set time. It's not.
I'm in New York and I eat dinner at 6pm sometimes. Other times I eat at 8pm.
Under UTC, this means that I sometimes have dinner on Wednesday at 23:00 and
other times I wait until Thursday at 01:00. Asking someone over for "dinner on
Wednesday" would always be ambiguous.

Here are some other confusing examples, if the dinner one doesn't illustrate
it:

(At work)

    
    
        "What days do you have off this week?" 
    
        "I got Tuesday/Wednesday and Friday/Saturday off"
    

(At school)

    
    
        "When is the paper due?"
    
        "Tuesday"
    
        "The class that starts on Tuesday or the 
        one that ends on Tuesday?"
    

There's a reason we have the days change when most of us are asleep. It's a
lot easier. A day encapsulates a day.

We could acclimate to all of this, sure. But we'd still have timezones. It
wouldn't be immediately obvious to the Londoner that 11:00 is a terrible Skype
time for her California colleagues (3am). So I don't see the gain here.
Dealing with time differences is a fundamental aspect of living on a ball
Earth.

~~~
coldtea
> _We could acclimate to all of this, sure. But we 'd still have timezones. It
> wouldn't be immediately obvious to the Londoner that 11:00 is a terrible
> Skype time for her California colleagues (3am)_

Yeah, I addressed that though. We'd still need to know the offsets sunrise-
wise or cultural-wise (e.g. 10pm is late to call in some countries, absolutely
normal in others).

> _So I don 't see the gain here._

It's trading local time reference points (like the sun etc), for global
coordination (in an increasingly interconnected and real-time planet) -- so
everybody immediately knows what time X is everywhere. It's not meant to
eliminate the fact that sunrise times etc are different, just to keep a stable
frame of reference without timezones for time (one would still need the
offsets to know whether it's night or day in place Y at time X).

> _Dealing with time differences is a fundamental aspect of living on a ball
> Earth._

Doesn't mean there's one and only one way to deal with those though. Or that
people don't spend a lot of time in the real-time, non-spherical, always-on,
web too nowadays.

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ktpsns
I 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 understood why culture and tradition is
an argument for inexactness.

~~~
Symbiote
> 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.)

~~~
FabHK
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](https://en.wikipedia.org/wiki/Metrication)

~~~
JacobJans
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?

~~~
merb
well in germany you still say "ein pfund" (one pound) or "halbes pfund" (half
pound) if you buy sausages/meat. but you mean 500g and not the real value of
one pound. it's just that this is used because we got used to it. we also have
a wierd system for the clock where we say "viertel vor" (a quarter to) or
"viertel nach" (a quarter past). which is pretty common to say the time in
quarters instead of values.

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frandroid
_When the bells of Big Ben — or any chiming clock that rings out the hours of
the day — chimes with one bell, we know that the first hour has just been
completed. As one commenter observes, having it ring zero bells wouldn’t tell
people what time it is. You can’t go from ringing eleven bells one hour to not
ringing any bells at all an hour later to then ringing one bell the hour
following the one in which you failed to ring any bells at all. People
wouldn’t be able to tell what time it was because of something they didn’t
hear!

Imagine this dialogue:_

    
    
        TOM: Oh good, it’s time for lunch!
    
        JERRY: Oh really, and how do you know that?
    
        TOM: Because it has to be noon, since I just now didn’t hear the clock!

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makecheck
You’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.

~~~
freehunter
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.

~~~
bradknowles
Time is hard.

Doing it right is really hard.

Whether this is measuring time or calculating time, it's hard.

------
romanovtexas
Fascinating. I've seen that at a lot of shops and places in Japan they go
beyond the 24 hours – indicating continuity in a way.

For example of a shop is open in the pattern –

Monday, January 8th 21:00 till Tuesday, January 9th 02:00

The Japanese signboards will denote it as -

Open on Monday, 8th Jan 21:00-26:00

I think it's we quite convenient and let's the people know that the shop's
time pattern sort of carries on from the previous day onto the next.

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DiThi
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.

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kbutler
The 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.

~~~
AnimalMuppet
No it doesn't. It makes exactly the same amount of sense to put 12:00 with
12:01 as it does with 11:59, because noon is not post meridian in exactly the
same way that is not ante meridian.

~~~
icedchai
Actually, it does make more sense to group them. You see that 12 at the
beginning of 12:00 and 12:01?

Most kids in the US are taught that 12 PM is noon and 12 AM is midnight in
elementary school. Though many understand this by first grade, I have been
surprised to encounter native English speaking 40+ year old adults that still
do not remember this. "Meet me at lunch at 12 AM!"

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fallingfrog
This 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?

