Talk:24-hour clock

"Military time" used to refer to 24 hour with decimal minutes

A friend of mine recently started working for the United States Postal Service, and she informed me that she was very confused by the military time used there, and that people in her workplace would sometimes just wait for the hour to come around before signing/clocking out so they wouldn't have to do the math.

Obviously this confused me, as I was under the impression (as is this article) that all it took to read military time is subtraction by 12 (or more pretentiously: perform rudimentary modular arithmetic =P).

When I looked at her schedule, however, I found that by "military time" the folks at the post office were referring to an odd system with 24 hours to a day and 100 minutes to an hour. E.g. on her work schedule "23:50" would correspond to 11:30pm in the twelve-hour system.

Is this usage common in the United States? In certain industries? Anywhere? MarcelB612 (talk) 02:30, 4 June 2010 (UTC)

Indeed in systems using "punching in" (and out) for registration of working hours, a division of the hour in 10 (or 100) units has been common. It makes calculating the hours worked much easier, since the subtractions (out-in), additions (totalling over days) and multiplications (hours times hourly wage) can be just done decimally, by hand or on any simple desk calculator. There is no need to convert to minutes. With the advent of electronic registration, these calculations can be done in the computer and are mostly back to hours and minutes. And by the way, "waiting for the hour" was done to profit from 0.1 hour (6 minutes) extra registered time. −Woodstone (talk) 09:46, 4 June 2010 (UTC)

Practical problems

How come is a practical problem that analog clocks don't display 24 hours? Most parts of the world have 12-hour clocks and use the 24 hour system... we are just so used to adding 12 that everyone understands 20h means 8pm without thinking about it. How can that be labeled as a 'practical problem'?? Same goes for the fact that striking clocks don't ring 23 times the bell at 23:00. Is it so important that it can be called a 'problem'? Loqu (talk) 19:48, 21 July 2010 (UTC)

Broken link

U.S. Government Printing Office, Style Manual is a broken link. Avihu (talk) 12:28, 23 July 2010 (UTC)

"Communication instructions – General, Allied Communications Publication ACP 121(H), Combined Communications-Electronics Board, April 2007" is also broken. Avihu (talk) 17:12, 23 July 2010 (UTC)

Fixed the first, tagged the second ([1]). Adrian J. Hunter^{(talk•contribs)} 03:53, 24 July 2010 (UTC)

Self contradiction ?

The article states: "Legal contracts often run from the start date at 00:00 till the end date at 24:00. It should be stressed, however, that "24:00" is a notation for the purposes of clarity and does not represent a distinct clock time." -- If it does not represent a distinct time, how does it add clarity ? I must be misunderstanding something...76.113.105.186 (talk) 09:29, 11 August 2010 (UTC)

It represents a well defined time: the very end of the specified day. It is not distinct from 00:00 the following day. But in a contract it is usual to specify the end as the last day it is still valid, not the first day it is not valid anymore. So from 1 Jan 00:00 till 30 June 24:00 would run precisely 6 months. Very clear and not confusing. Much better than stating from 1 Jan 12 a.m. to 30 Jun 11:59 p.m. (not totally clear about the first half day and the last minute). −Woodstone (talk) 12:22, 11 August 2010 (UTC)

23:59:59 represents an accurate time, but my understanding is that there is no 24:00:00. The time goes from 23:59:59 to 00:00:00 to 00:00:01. Since there is no 30 June 24:00, the six month period would never arrive. A more accurate phrase may be from 1 Jan 00:00:00 through 30 June 25:59:59 or until 1 July 00:00:00. Tesseract501 (talk) 16:04, 6 December 2010 (UTC)

Unless we are referencing military time. My understanding is that midnight is called 24:00:00, with one second after midnight being 00:00:01. Tesseract501 (talk) 16:08, 6 December 2010 (UTC)

Yes there is a June 30 24:00 and it is exactly equal to July 1 00:00. Midnight, being the boundary between two days, can be seen from two sides. It is one instant with two notations. The ISO standard is fully clear on this. A physical clock would not show 24:00 for an infinitesimal instant, but jump immediately to 00:00 (although some appear to actually show 24:00 for the first minute). −Woodstone (talk) 18:30, 6 December 2010 (UTC)

Let me try and enlighten you

It appears from this article as well as the 24 hour clock article, which I will cc this comment to, that most if not all editors on this subject have missed the concept of a clock completely. Though, it is understandable to me because I myself did not make this realization until recently.

It is quite amazing to see that the creators of this ancient time measurement system seemed to understand this deep fundamental concept and was never questioned. While now all these smart anonymous editors don't even sense the concept rushing past them due to their weak reasoning.

Now that I am done being rude, caused by the confident, yet wrong, content of this article, let me prove my worth; though I will warn you I am not good at transcribing my thoughts to natural language; I will try my best; please bare with me.

The first thing to understand is that there is no such thing as Time = zero. When Time = zero it means you are dead. It does not exist because time only exists to you because you are alive to perceive it. In other words, the moment in time is a function of your unitary perception of all the preceding time before that moment such that your unit of perception is to the power of e.

Heh, let me try and explain that again. T = f(x):=e^x So when you born, that absolute infinitesimally tiny moment when you perceive life. That is one unit of time, as soon as you continue to live for another one of those units of time, that is now the second unit of time. http://en.wikipedia.org/wiki/E_(mathematical_constant) see this article for help understanding what I mean. Time would be the Y in the graph. As soon as you first perceive life, when x=0 time is 1. This is why there is no year zero. This is why there is not time 0:00 on a 12 hour clock. This is why I think a 24 hour clock is strange. Having time go from 23:59 to 24:00 then to 0:00 then to 0:01 makes no sense unless you share 1 second between 24:00 and 0:00.

There is a comment somewhere that says it is ambiguous as to whether midnight is the start or end of the day, yeah, no shit. You tell me what it is! A day is not an isolated universe of time, it is part of a continuous fabric of time that has not start or end. The end of the day is the start of the next day, there is never a moment when Time = zero as soon as the big bang happened time was 1 and has been increasing ever since. Time was 1 if you think that there must be a fraction of a moment before that first 1 then whatever fraction you are imagining would be the unit of time so that would be 1. As soon as there is existence time has already been created and it's increasing.

The present is an infinitely small moment of time that is imperceivable, as soon as you notice it, it has already passed. You exist physically in the present but your mind exists by watching time fly towards you and then past you into the past as it gets locked into the memory of the universe and irrevocably stamps it's impact on all future events.

This can be intuitively seen and understood by every person. We all know that each year of our childhood felt very long. And as you get older every year seems to go by so much faster! This concept shows up in pop culture with sayings from kids like, "Are we there yet?" and old people such as, "It was just like yesterday."

The reason this is is because say you live for 1 year. Then you live 1 more year. You just doubled your life! As far as you are concerned you just lived for forever! Twice! Which becomes the new forever. And as you become 50 once you live one more year that is no longer as large an amount of time. It is only 1/50th what it used to be.

So the reason 12:00 the one that happens during the daylight where you are. Is called 12:00 pm is because as soon as 11:59 ticks one unit to 12:00 there is units less than a second we cannot comprehend that have already begun counting up. Once they reach 1 second it becomes 12:01 pm which is clearly the afternoon. So since some people like to clarify 12:00 when it is sunny with 12:01pm and not just 12:00pm, just think it is really 12:00:00:00:00:00:00:01 the moment it flips from 11:59 am.

That is why there is no 0:00. And I would love to hear from some electronics engineer explain how a 24 hour clock can display both 24:00 and 0:00. I did not realize time did not exist for 1 second everyday. I just am not sure if that second is at the 24th hour or the zeroth hour. Heh, zeroth hour, funny people and their made up symbolic lies.

I like how people think that when zero was realized to be a number they think that means it can exist. I'm sorry, zero does not exist. That is what zero is, none existence. It is what is inside that little circle we use to show it's concept. If you have 4 apples, and you give away 4 apples you don't walk around with a special magical apple known as your zeroth apple. You walk around empty handed saying, "I have zero apples!"

That is why the month does not start on day zero and then move to day 1. The month starts on 12:00am actually. Which is also the end of last month in our macro world. Maybe some electrons get to tunnel into that zeroth second and freeze in time for who knows how long then popup somewhere else randomly. But that's the great thing about the universe! It's made up of real existence held together by irrational imaginary chaos.

Maybe that's where my mind lives, I hope you can join me there too and not just try to argue unsuccessfully against me. Because I would love to hear a justification on how, "The rollover from 12 to 1 happens an hour later than the change between a.m. and p.m." this sentence is even remotely disadvantageous.

I forgot to sign, that would have been a shame, eh? Rukaribe (talk) 12:11, 29 October 2010 (UTC)

I'm afraid you have completely failed to understand the real numbers. Quietbritishjim (talk) 02:29, 18 November 2010 (UTC)

Having read a few more lines of your comment (why did I subject myself to that!?) I now realise it's an elaborate troll (maybe that's a bit harsh; it seems like you're parodying something, but I don't know the background). Still, in the spirit of good faith, I'll leave my original reply up there. Quietbritishjim (talk) 02:36, 18 November 2010 (UTC)

So how many lines have you read in total after your second comment then? It is not the most rigorous piece ever written and is quite condescending but I do know of the real numbers. They are just damn confusing. Thanks for at least thinking it was elaborate but unfortunately I am no troll, I am quite serious though my meaning may be lost in my poor natural language and disjointed thinking.

After reading my comment again: I think it is important to keep in mind the context of where my mind was when I wrote this. It was in relation to the enumeration and display of time as defined sets of positive integers. You say I do not understand the real numbers, you are correct I find them quite mind blowing. But I think that is beside the point, the point is you have constructs involved in this situation that cannot be fully explained by mathematics currently. Trying to understand time means you need to understand life I feel.

I wish you didn't just think I was some troll because I think there is more here than you may admit. Time is a ring, with any moment of time you define the end of it is the beginning of the next one. That is what I said when I said every months starts on day 1. Every week starts on the 1st of 7 days, not the 0th of 6, like I said if time is zero then time has stopped and you must be dead. The real numbers may explain this in a normal system but the boundary of time is undefined. In order to know what time is like when it is zero, algebraically you would need to divide by zero to learn that at some point and we all know that cannot be done.

Clocks cannot show real numbers, that is my point. Instead we created a looping system with different magnitudes of looping based on real physical events at our scale. If anything it would have been best if they just slowed clocks down and made each hour a half hour and had 12 hour days with one revolution of the hands about the face. It may seem like an odd idea but that is mostly because traditional time is so ingrained in us now it would seem strange. But I think it would be a good system if we knew of nothing else and could start fresh. I also think we should have a universally defined unique symbol for each month and day of the week that is as powerful as numbers and letters in terms of semantics. That would make dates in computers so much easier assuming a proper encoding system was created in this hypothetical world in my head.

So, if you ever do reply again. Do you think we should start counting time at zero? Can you explain why a 24 hour clock can have a time 24:00 and 0:00 without gaining and extra second? Will you actually read my complete comment and try and unearth what I am trying to say? Because I'm pretty sure if you overlook whatever errors I make in the details my overall philosophy might seem pretty compelling. Cheers! Rukaribe (talk) 19:26, 25 November 2010 (UTC)

Whatever that may be about, it's not about improving this article. — Arthur Rubin (talk) 21:03, 25 November 2010 (UTC)

I have read your comments. I will reply properly, but it's a bit late at night for me to do it right now. For now I will say three things: (1) I stand by my original (first) comment (2) I agree with Arthur Rubin (3) I will ask about an analogy to try and help figure out your thinking:

Most people would consider time (even the 24 hour clock that measures it) as real numbers. This is just like e.g. distance. So imagaine I'm 10km away from you, and as you walk towards me there's 9km between us, then 8km, then 7km ... then 1km, then finally we're at the same point so we're 0km apart (ok so you'd leave some personal space, but in principle we could get pretty close). Would you say that there wasn't really 10km between us at the start because that doesn't include zero? That there was really 11km between us (but then there would have been 12km by the same reasoning, etc)? Or do you consider this example doesn't work because we couldn't really be 0km apart, and that's your whole point? Quietbritishjim (talk) 00:47, 26 November 2010 (UTC)

First, I feel it can help improve the article by explaining an overall reasoning for why the 12 hour clock exists the way it does. It just seems there are a lot more people on the 24 hour clocks side on the internet.

As far as your example the issue there is you have two different objects converging. With time it is looping back to itself which is what makes time so odd. Also with the dimension of space a length always has a definite beginning and end. It may be relative to where you define the point of origin but there is always a definite magnitude that can be represented with a real number like you said. Like with a finite value of an infinite series.

The special issue with time is that time in your perception on exists once you exist. So as soon as you are alive, whatever that is, then time has already started. I think of it kind of like an annuity. You have annuities due and annuity immediate an annuity due you make a payment at the beginning of the month while an annuity immediate you make at the end of the month (if you are the investor). When I learned about these in school they called the annuity immediate an ordinary annuity for simplicity because the word immediate makes it sound like it would supersede an annuity due. The reason they use this terminology is because an annuity due as soon as it is legally agreed to, is already due. The infinitesimally small moment after you create it, it was due and you are already technically late but humans are nice and give minor grace periods. While the annuity immediate is due immediately at an up coming time, which is usually a month.

This is part of the same concept, how there is no moment to experience time zero. Because it's zero, there is no time then so you can't enjoy that moment of zero time. It doesn't exist by definition and you can never experience it. This is why interest is compounded by the exponential function also because it is purely a function of time while humans are alive and creation economic growth by creating capital from our attempts to reduce entropy.

So back to your point, you did predict my reply. Since there are two objects here they can never be in the exact same location and they will never be at 0km. The Pauli exclusion principle demonstrates why this is nicely.

Also do you mean to say originally that I don't understand rational numbers? You seem to be using those to explain your example and not real numbers, to me it seems the real numbers actual help explain what I am saying more so. Such as e and pi combining to explain the looping aspect of time as it continues at some rate. My view also fits nicely with relativity as far as I can tell without getting into it too far.

Anyways, this is probably not helping the article so I will cite some simple corrections. The main one is the claim that there is confusion whether 12 noon is 12:00am or pm. I see no confusion here, it is pretty clear since as soon as 11:59 ticks over to 12:00 it has switched to the afternoon, this is when the sun is directly overhead so it makes sense. You can think of 12:00 counting to 12:59 then 1:00 as going from your time 0 to time 1 on a scale of hours with fractional minutes. The key is that it is also the last hour of the prior half day break. The only reason this happens is because you never truly are at time 12:00 because as soon as you reach it you pass it and are a millisecond into the afternoon.

Days work differently because a day does not get a fractional time period attached to it. It exists as it's own unit which starts at one and goes until the end of that month. You can think of a day like an annuity due where an hour is an annuity immediate because we can just keep making more precise rational numbers as units of time and then put a colon between them and the prior units. Based on that convention you can break time down as much as you want, but you will never get to time = zero.

From what I read the only reason 24 hour clocks show 0:00 and 24:00 is for convention to reduce the inherent ambiguity. The issue is how the circuit is coded. Do they just make 0:00 and 24:00 last half as long as normal? Or do they just alternate each day with which notation they display at that moment. I wrote this originally for the 12-hour article mostly because it does contain many odd statements. I like this one particularly, "The rollover from 12 to 1 happens an hour later than the change between a.m. and p.m." it is listed under the header of "Criticism and practical problems". I am not even sure how to address this statement really. So the writer thinks it makes more sense for 12:00 to count all the way up to 12:59 then switch to pm when it ticks over to 1:00? How do you even respond to that? Since 12:00 is the end of one day or half day and the microsecond later the start of the next why would you let 12 count up? It's simple, If time > 12 then it's crossed over into either the second segment. It doesn't matter if it's 1 minute past 12 or 1 micro second. It's still crossed the 12:00 mark and is not approaching 1:00. Anyways, I feel like I'm beating a dead horse at this point now.

I hope you are starting to see my point because I think it may be more fundamental and provider deeper explanation than you gave it initial credit. It's just a shame I suck at transcribing my thoughts I guess. Rukaribe (talk) 02:37, 26 November 2010 (UTC)

To answer an implied question: A 24-hour clock almost always shows 00:00. 24:00 is a convention to show midnight of the next day, in cases where, say the time interval, 23:00–00:00 looks odd.

And the question of, on a 12-hour clock, whether noon is 12 am or 12 pm, only applies to noon itself. 12:01 pm is in the afternoon, but 12 pm may be ambiguous, and possibly 12:00 pm. — Arthur Rubin (talk) 16:28, 26 November 2010 (UTC)

There is no implicit questions in my comment if that is what you mean. I'm not sure what makes you think I am implying a question that you must answer for me so please don't read my comments in a manner of presumed ignorance on my part that you must correct. Rather, read it in a fair an open manner. You can presume I am a horrible writer based on the evidence if you wish. But please do not presume ignorance.

You can see I said, "...and 24:00 is for convention to reduce the inherent ambiguity. The issue is how the circuit is coded. Do they just make 0:00 and 24:00 last half as long as normal?". You have not answered anything I can even extrude into an implied question. I started that it appears to be a convention which you confirmed, thanks. But the question I overtly asked on the technical merits of the implementation of this convention which are quite important for the defense of this article. A clock cannot simply add in a whole extra minute of falsely displayed information and claim to be even remotely accurate for any situation. Like I said they would need to make 0:00 and 24:00 both half as long or never show 0:00 and go straight to 0:01 after 24:00. That would be a useful answer.

The fact that the 24 hour clock needs to be literally wrong by convention to improve it's interpretation is not a benefit in my eyes. It says that the clock needs to be incorrect to be easier to use, yet this article is written in a condescending pompous manner in which individuals who use the 24-hour clock view themselves as smarter and superior to users of the 12-hour clock. When in reality I just demonstrated that the 24-hour clock is only superior for people with a lack of understanding of how time works. I'm trying to be nice after the condescending comments and whole article in general.

The last thing you said I do not quite get what you are trying to say. I think because you put noon in quotes and I don't know what you are trying to get across with that unspoken emphasis. But I think you missed the point of my explanation. Think of it like this, there is no such thing as 12. As soon as you hit 12 a tiny amount of time passes and you are not one second into the first minute of the 12th hour of the day. That means you are over 50% into the length of the day and therefor in the afternoon. You can confuse this am pm thing with every hour of the day since the 12 hour clock splits the way in half and repeats the notation with an operation identifier to clarify which half. This is a good argument for the 24 hour clock and better than most of the others listed.

Like I explained with my annuity due example, the proper manner to handle this situation in places like contracts would be to clarify whether the stipulation is due at the start or end of the time interval listed. This would clarify the incomprehensible tiny moment of time when the stipulation is due and at which end of that immeasurable moment it is due. This isn't quite necessary since seconds are usually accurate enough.

To the last thing you said, you are mixing up the idea of ambiguity and incorrectness. It is not ambiguous whether the notion of noon is 12 am or pm if you understand the concepts I explained above. 12:00 is the start of the half day as well as the end of the previous half day. When you go from 11:59 to 12:00 it switches over and since the morning is understood to be the am then when it switches to 12 it is the pm the moment that happens. You are not truly at 12:00 you are at 12:00:00:00:00:01 or however accurate you want to get. This should be obvious and clear, everyone knows 12:01pm is the after noon. Everyone should similarly know 12:00pm is the afternoon for the same reason. I'm sorry if you think this is ambiguous, I think it's just lack of understanding. If you wish the 24-hour clock is more user friendly for un-knowledgeable people by all means do that. But don't act like you are superior because you use the 24-hour clock because that does not appear to be the case.

Sorry if you find that rude but I am simply following the golden rule and reacting to your comments. —Preceding unsigned comment added by Rukaribe (talk • contribs) 02:55, 7 December 2010 (UTC)

Nice rant. It has nothing to do with improving the article, but it is a nice rant. There's no "half-minute" in 24-hour clocks showing 00:00 or 24:00. Most show the former, but some apparently show the latter for one minute. Now, there does seem to be an anomaly in 12-hour clocks if you consider the change from 12:59 to 1:00 to be significant, as it is different from the change between am and pm. — Arthur Rubin (talk) 16:54, 7 December 2010 (UTC)

Thanks! As per improving this article I think it is best to consider all written here to apply to this article as well as the 12-hour clock article which I linked to. Since that article is written to basically make 12 hour clock users appear inferior it's not from a neutral point of view in my mind and all the reasons I outlined clarify why that is I feel.

The am pm change you just mention does not matter, you can switch from am to pm and vice versa whenever you choose as long as the two times are equidistant apart for the total length of the day. The reason it happens are 12 and not 1 is because it's to show the hour is not the smallest unit of time we use. In reality it should happen at some tiny fraction of a second after 12 and the exact precise time of 12 should be neither am or pm but we can never exist then. That makes no sense though and is caused by the 12 hour clock, if that creates the ambiguity in your mind then I see your point.

My point is that if you think of it such that as soon as it becomes 12:00, already 1 millisecond has passed, so it is now passed 12 and into the afternoon. I tried to explain this concept with the annuity due and annuity immediate example. Think of the time like a loop and the end of the day is the start of another. That is why you cannot say 12:00 is the start or end of the day definitively unless you also specify the day. Any ambiguity is more so caused by the lack of a date than whether it is morning or afternoon. If anything the mental math needed to do is more ambiguous than that to most people. Well from where I am from anyways where 12-hour clocks are most common. Really though, who likes to subtract 12 from 17 and 19? Yuckie.

Also, I have no idea when they first started the first official clock whether they started it at 12 or 1 but I think that would be interesting to learn. :)

Rukaribe (talk) 22:34, 3 January 2011 (UTC)