Am/pm

[Guest cinta]

My Maths teacher thinks that there is no such thing as 12am or 12pm... That according to his 'Maths Texts' they are only called Midday or Midnight - we've tried to prove him wrong but he is standing steadfast... Does anyone here have any answers to his 'theory'? And if so, do you have any proof that I would be able to show him??? Thanks, LT

[Skye]

Get a clock with a circular face and point out the number between 11 and 1.

[Runner]

You would not be able to say neither 12:00 am nor 12:00 pm as it would be exactly from that point we measure from, however, when it is a second past the 12:00 mark it would turn into 12:00 am. You can definitely not say 12 pm because the pm indicates that it is before twelve.

[greg1917]

Its a minor and ultimately irrelevant point. maybe your maths teacher should concentrate on teaching maths because it looks like hes just trying appear like the wise old owl due to a technicality of language. Not particularly impresssive for a teacher.

[VendingMenace]

actually, i think he IS teaching math by saying this. I think he could be trying to make the point that the function of time is not continuous. It has discrete changes AM to PM. Thus, depending how you approach the am/pm barrier (from forwards or backwards) one 12 oclock time may appear to be either am OR pm. It is becuase of this sharp break in the graph of time, that this strange duality occurs (and hence there really is no 12am or 12 pm).

 

Of course, we only travel forwards, so this seems a mute point to most people. However, i think that the concept is well demostrated by using something as commonly encountered as time.

[YT2095]

Hmmm... Interesting, perhaps if you explained it in terms of the 24 hour clock?

maybe that would help

00:00 to 11:59:59 being AM and 12:00:00 till 23:59:59 being PM?

at least that`s how it`s worked out and understood in the millitary

[swansont]

12 AM or PM is ambiguous and incorrect. It's either 12 Noon or 12 Midnight.

 

click here

[YT2095]

When a specific date is important, and when we can use a 24-hour clock, we prefer to designate that moment not as 1200 midnight, but rather as 0000 if we are referring to the beginning of a given day (or date), or 2400 if we are designating the end of a given day (or date).

 

To be certain of avoiding ambiguity (while still using a 12-hour clock), specify an event as beginning at 1201 a.m. or ending at 1159 p.m., for example; this method is used by the railroads and airlines for schedules, and is often found on legal papers such as contracts and insurance policies

*taken from the above URL*

pretty much what I said *taken from the Millitary*

[Francois Demers]

My Maths teacher thinks that there is no such thing as 12am or 12pm...

 

 

AM stands for "Ante Meridiem" and "Post Meridiem", Latin for "Before" and "After" the middle of the day which is deemed to be the instant when the Sun is due South in the sky. There is archaelogical evidence for this convention dating back to 1500 BC, when solar clocks were just about the only way to measure the passage of time with socially-useful accuracy.

 

The convention eventually fell into disuse at the beginning of the 17th century, when labelling from 00:00 to 23:59 became more popular, except in British colonies.

 

Any time-labelling system is a convention. The "am pm" convention is, by far, the most-used in the USA.

 

Claiming that there is no such thing as 12AM and 12PM is the same as claiming there is no such thing as dollars (the name of the currency is a social convention), pounds, or miles (the names of units of mass and distance are social and legal conventions) . In this, as in other linguistic problems, usage rules.

[swansont]

AM stands for "Ante Meridiem" and "Post Meridiem", Latin for "Before" and "After" the middle of the day which is deemed to be the instant when the Sun is due South in the sky. There is archaelogical evidence for this convention dating back to 1500 BC, when solar clocks were just about the only way to measure the passage of time with socially-useful accuracy.

 

The convention eventually fell into disuse at the beginning of the 17th century, when labelling from 00:00 to 23:59 became more popular, except in British colonies.

 

Any time-labelling system is a convention. The "am pm" convention is, by far, the most-used in the USA.

 

Claiming that there is no such thing as 12AM and 12PM is the same as claiming there is no such thing as dollars (the name of the currency is a social convention), pounds, or miles (the names of units of mass and distance are social and legal conventions) . In this, as in other linguistic problems, usage rules.

 

So, is noon before or after the middle of the day? This is analogous to a coin landing on its edge — is it a head or a tail? Is zero a positive or negative number?

 

If you click on the link I provided before (well, seven years ago), you'll note it's from NIST, i.e. the national standards lab. It's the official position of both them and the US Naval Observatory, who jointly keep the official time in the US. 12 AM or 12 PM is ambiguous. There is no fully-accepted convention for which means noon and which means midnight. It's too easy to make a mistake, which is why the notations are to be avoided.

[TonyMcC]

Hmmm... Interesting, perhaps if you explained it in terms of the 24 hour clock?

 

maybe that would help

 

00:00 to 11:59:59 being AM and 12:00:00 till 23:59:59 being PM?

 

at least that`s how it`s worked out and understood in the millitary

In the British military using the 24 hour clock the terms AM and PM were never used (not being necessary).

For the sake of clarity for all routine matters such as changing guard duties the time between 23.59 and 00.01 was never used. (Both times assumed to be midnight). i.e. 23.59 on the first of the month being the same time as 00.01 on the second of the month.

[imatfaal]

Tony - same convention of avoiding 0000 is used in shipping with certain arrangements for which 'incorrect' version you use - you arrive at 2359 and you sail at 0001; the option starts at 0001 and closes at 2359; hire payments start at 0001, finish at 2359 and 24 hours have elapsed in between.

[MR. Science]

Who is this teacher,where do you live,what school do you go to, this will tell me a lot, since it might me what region your in...

[D H]

There is no fully-accepted convention for which means noon and which means midnight. It's too easy to make a mistake, which is why the notations are to be avoided.

From a pedantic point of view I do agree that designating noon 12 pm is a bit nonsensical. That abbreviation "pm" means "after noon", after all. How can noon be after noon?

 

However, the US Government Printing Office, and your own digital clock (assuming you have a 12 hour digital clock), beg to differ: 12 pm is noon, 12 am is midnight. One minute after noon, 12:01 is 12:01 pm. Similarly 1 second after noon is 12:00:01 pm, and 1 microsecond after noon is 12:00:00.000001 pm. When your digital clock shows 12:00 pm it is almost always showing the correct time because what that really means is that it is somewhere between noon and 12:01 pm.

 

 

 

[ydoaPs]

It is a rather odd convention. 12am is followed by 1am. Who came up with that?

[D H]

It is a rather odd convention. 12am is followed by 1am. Who came up with that?

All the times between midnight and 1 am are 12:something am. One nanosecond after midnight is 12:00:00.00000001 am. Insert as many zeros as you want (a finite number) after the decimal point and it is still am. The only point in contention is midnight itself.

 

We are being overly pedantic here arguing over those two infinitesimally small instants, noon and midnight. Pedantry is a disease to which mathematicians, scientists, and engineers are highly susceptible. Sometimes it is best to stop being the pedant. This is one of those times.

[ydoaPs]

All the times between midnight and 1 am are 12:something am. One nanosecond after midnight is 12:00:00.00000001 am. Insert as many zeros as you want (a finite number) after the decimal point and it is still am. The only point in contention is midnight itself.

 

We are being overly pedantic here arguing over those two infinitesimally small instants, noon and midnight. Pedantry is a disease to which mathematicians, scientists, and engineers are highly susceptible. Sometimes it is best to stop being the pedant. This is one of those times.

The military solves that issue nicely. 2359 is followed by 0000.