Why does the 12h clock start at 12:00, not 0:00?

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08 Aug 2024, 9:41 am

The 24-hour clock starts at 0:00, not 24:00. So why does the 12-hour clock start at 12:00 and not 0:00?



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08 Aug 2024, 10:26 am

00:00 is midnight when it starts. Then goes 01:00 at 01AM etc. It is a MUCH easier system to use.



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08 Aug 2024, 12:51 pm

I would blame zerophobia. Humans instinctively avoid zero.
Like how in the US, we have no "ground floor", the ground floor is called the first floor. In other countries they do have a ground floor but they refuse to call it the zeroth floor, which is what it is.
Or on keyboards, the zero goes at the end instead of the beginning where it belongs, like it was just added as an afterthought.


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08 Aug 2024, 2:17 pm

I live in Canada, but I find the 24 hour clock confusing. Maybe it's because of dyscalculia. I was maybe 12 by the time I could fully understand a non-digital clock. Also people would tell me things like "It's half-past 10" instead of "10:30", which also confused me.



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08 Aug 2024, 2:38 pm

Ummm... Surely the 12 hour clock starts at 0:00 AND 12:00



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08 Aug 2024, 2:44 pm

The 24 hr clock is used on the railway and by the military etc where clear accuracy is essential. The main reason why it is confusing for some is that they are simply not used to it.
The easiest way to learn quickly how to use it is if one wants to convert from 24 to 12 and it is in the afternoon is to take off two and then subtract by ten. The reason why I say to do it this way is the mind works quicker doing that. By working it out the other way then simply add two and then add ten.

After a while ones mind thinks in 24 hrs rather than thinking 12. One will find it easier thennas bus or train timetables come natrually without thinking!



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08 Aug 2024, 2:53 pm

Because that's the way the pea rolls.


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bee33
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08 Aug 2024, 4:06 pm

If the 24-hour clock didn't have 0:00 it would have 12:00 twice, so it has to be that way. As for the 12-hour clock, using 12:00 instead of 0:00 is more pleasant and more logical, since there isn't actually an hour zero.



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08 Aug 2024, 4:39 pm

bee33 wrote:
If the 24-hour clock didn't have 0:00 it would have 12:00 twice, so it has to be that way. As for the 12-hour clock, using 12:00 instead of 0:00 is more pleasant and more logical, since there isn't actually an hour zero.


With the 24 hr clock it is 00:00 and not 0:00. :D



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08 Aug 2024, 5:06 pm

Peas porridge hot
Peas porridge cold
Peas porridge in the pot
nine days old
Some like it hot and
Some like it cold and
Some like it in the pot
nine days old

Some like to start with zero: if you measure with a ruler you can start with 0 inches and 1/4 inch then 0 inches and 1/2 inch and then 0 inches and 3/4 inch then 1 inch.

Some like to start counting with 1. If you count on your fingers you start with 1 finger, then 2 fingers then 3 fingers then 4 fingers.

Both 24 hour clocks and 12 hour clocks “wrap around”. The hour after Jan 1 23:00 is Jan 2 00:00.
A 12 hour clock follows 12 o’clock with 1 o’clock.

On a 12 hour clock 12 follows 11 and 1 follows 12. On a 24 hour clock 23 follows 22 and 0 follows 23. Both go in circles and don’t really “start” anywhere.

I simply tell my kids: “PM” means “afternoon”. Obviously 12:01 is after noon. So is 12:02. So with 59 distinct numbers (up to 12:59) of minutes being “PM” and all starting with 12:?? They simply made 12:00 “PM” too so it wouldn’t be lonely. And the same with “AM”.

Old ways die hard.

Why is the “h” in “hour” silent? Why is “minute” a bigger word than “hour” if an hour is more than a minute? And “day” is shorter still.

Why schmy??? Why not???


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Last edited by Fenn on 08 Aug 2024, 5:18 pm, edited 1 time in total.

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08 Aug 2024, 5:18 pm

bee33 wrote:
If the 24-hour clock didn't have 0:00 it would have 12:00 twice, so it has to be that way. As for the 12-hour clock, using 12:00 instead of 0:00 is more pleasant and more logical, since there isn't actually an hour zero.

It's actually not more logical. In math you count 0, 1, 2, etc. But on clocks you count 12, 1, 2, etc. That makes no sense. 1am is 1 hour after midnight, 2am is 2 hours after midnight, so it makes sense for 0am to be 0 hours after midnight. And it's only more "pleasant" if you're zerophobic. Hasn't zero experienced enough discrimination? :D

If we're being more technical, clocks are an example of modulo arithmetic. In modulo 12 there are only 12 integers, and when you count higher it circles around to the beginning. In theory mod 12 arithmetic would work equally well if you counted from 0 to 11 or from 1 to 12, but the convention is to go from 0 to 11 because it makes math a lot easier. For example, 0*0=0, 0*1=0, 0*2=0, etc. which follows the same rules we're used to. But if you said that 12*12=12, 12*1=12, 12*2=12, etc. that would be weirder and less intuitive. Another way to think of mod 12 is that a number is the remainder when it's divided by 12, and if a number divides evenly into 12 its remainder is zero. (e.g. 72/12 is 6, not 5 with remainder 12) It also makes decimals more intuitive, because numbers like 0.5, 0.273, 0.689523 fall between 0 and 1, so it makes sense for them to begin with 0. If they fell between 12 and 1, it would be confusing to have 12 followed by decimals beginning with 0 (but no actual 0), or alternatively, even more confusing to have 12.5, 12.273, 12.689523 followed by 1 (which is the way the clock works, and it makes no sense at all.) This is easier to understand in mod 10, where a number is equivalent to its last digit (and decimal places). 21 becomes 1, 20 becomes 0, 20.689523 becomes 0.689523. When viewed mathematically this convention makes much more sense.


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08 Aug 2024, 5:23 pm

utterly absurd wrote:
bee33 wrote:
If the 24-hour clock didn't have 0:00 it would have 12:00 twice, so it has to be that way. As for the 12-hour clock, using 12:00 instead of 0:00 is more pleasant and more logical, since there isn't actually an hour zero.

It's actually not more logical. In math you count 0, 1, 2, etc. But on clocks you count 12, 1, 2, etc. That makes no sense. 1am is 1 hour after midnight, 2am is 2 hours after midnight, so it makes sense for 0am to be 0 hours after midnight. And it's only more "pleasant" if you're zerophobic. Hasn't zero experienced enough discrimination? :D

If we're being more technical, clocks are an example of modulo arithmetic. In modulo 12 there are only 12 integers, and when you count higher it circles around to the beginning. In theory mod 12 arithmetic would work equally well if you counted from 0 to 11 or from 1 to 12, but the convention is to go from 0 to 11 because it makes math a lot easier. For example, 0*0=0, 0*1=0, 0*2=0, etc. which follows the same rules we're used to. But if you said that 12*12=12, 12*1=12, 12*2=12, etc. that would be weirder and less intuitive. Another way to think of mod 12 is that a number is the remainder when it's divided by 12, and if a number divides evenly into 12 its remainder is zero. (e.g. 72/12 is 6, not 5 with remainder 12) It also makes decimals more intuitive, because numbers like 0.5, 0.273, 0.689523 fall between 0 and 1, so it makes sense for them to begin with 0. If they fell between 12 and 1, it would be confusing to have 12 followed by decimals beginning with 0 (but no actual 0), or alternatively, even more confusing to have 12.5, 12.273, 12.689523 followed by 1 (which is the way the clock works, and it makes no sense at all.) This is easier to understand in mod 10, where a number is equivalent to its last digit (and decimal places). 21 becomes 1, 20 becomes 0, 20.689523 becomes 0.689523. When viewed mathematically this convention makes much more sense.


Yes, exactly. The first minute of every hour is 00, not 60. The first hour should logically be 0, not 12.



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08 Aug 2024, 5:58 pm

With code is is not all that tricky.

Code:
$ ( echo 7:23 PM ; echo 7:23 AM ; echo 12:23 PM ;echo 12:23 AM ; ) |
awk -F$'[:\040]' 'BEGIN {ampm2hh["AM"]=0;ampm2hh["PM"]=12;}
{h=$1;m=$2;ampm=$3;
printf("%02d:%02d ::: original %s\n", (h%12)+ampm2hh[ampm], m, $0)}' |
LC_ALL=C sort -u
00:23 ::: original 12:23 AM
07:23 ::: original 7:23 AM
12:23 ::: original 12:23 PM
19:23 ::: original 7:23 PM


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09 Aug 2024, 12:07 pm

Somebody thought of it.
And someone believed it.
And look what its done so far.

- Kermit the Frog, The Rainbow Connection


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09 Aug 2024, 12:53 pm

The "problem" (if it is a problem) is that (a) the ordinal number names(first, second, third, ...) are derived from the names of the counting numbers (one, two, three, ...). And (b) "zero" was not recognized as being any kind of "number" in any civilization until the last few centuries. Long after the counting numbers were invented.

The Hindus invented the zero, and it was adopted by the Muslim Arabs in the Middle Ages into their decimal number system, and finnally that number system spread to Christian Europe, but not till maybe the 1200s AD. Before that Europeans had no concept of zero, and thus no talk of a "zeroth" thing in a sequence.

When the Vatican set up our calendar dating system they started the years with the supposed b-day of Christ. But the system was invented in 525 BC (long before the concept of "zero" arrived in Europe). So the first year of Christ's life was "the year one" (not the year zero), and all of the years of the first century after Christ are called "the first century" even though they go from 001 to 099. Which is why we live in the 21st Century despite the fact that the year 2024 starts with "20" and not "21".



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10 Aug 2024, 12:54 pm

That would make sense if anyone ever talked about a baby being a year old the day he was born.

https://en.m.wikipedia.org/wiki/Fraction

Look at the “History” of fractions. 0 for counting is not quite the same as 0 for calculating or 0 as a place holder in a number such as 60. The Egyptians used Egyptian fractions c. 1000 BC.


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