Talk:12-hour clock

Abbreviations

The section titled "Abbreviations" has no cites and I couldn't find any mention of the PD an MD in Albanian on a Yahoo! search other than Wikipedia and its forks and mirrors. Zginder 00:46, 29 August 2007 (UTC)

Yeah, besides being cute (I'd love to call 8am "eight-pi-mu" and 3pm "three-mu-mu"), this section is redundant, unsourced, and completely unnecessary. I strongly suggest deletion. -- Tkgd2007 (talk) 22:34, 10 April 2008 (UTC)

"...one must fall back on one's cultural literacy to disambiguate". Besides not passing the laugh test, it is an overstatement of the situation. It is taking something rather elementary and making it appear difficult. JackOL31 (talk) 15:32, 1 January 2010 (UTC)

"The use of a.m. ... can be confusing because am is an English word, AM ...amplitude modulation and A.M. ... anno mundi, in the year of the world, and for Master of Arts". This is an example of excessive criticism. Context clues can not be ignored and we cannot frame this from the perspective of a clueless person. All abbreviations are typically used within a context where the meaning is clear. This article uses BC and AD, however I don't see any criticism that those might be confused with - British Columbia, Book Club, Birth Control, Boston College, Bar Code, Before Christmas, Bankruptcy Court, Board Certified, Birth Certificate and Birth Control -or- Assistant Director, Associate Director, Active Duty, Attention Deficit, Associate Degree, Air Defense, and Assistant Deputy. Also, the mention of the recommendation for a space between the time and a.m./p.m. is sufficient. There is no proof that it is widely ignored (and violated is too strong a word for a stylebook convention). Lastly, combined similar concepts into a single paragraph. JackOL31 (talk) 02:43, 5 January 2010 (UTC)

Introduction section

The sentence regarding the am/pm variations is redundant. The Abbreviation section addresses the topic in detail. I'll remove the redundant information. JackOL31 (talk) 18:08, 13 December 2009 (UTC)

There is a sentence which says that the indication of noon and midnight is disputed. I cannot find any verification for this statement. I see where there is confusion, especially where the 24-hr system is predominant, but never any documented dispute. For manufacturers of timepieces with an am/pm indication, I have consistently seen the 12 o'clock hour displayed as shown in the table. Could someone cite references documenting a dispute involving the correct designations for the 12 o'clock hour? JackOL31 (talk) 18:48, 13 December 2009 (UTC)

In the accompanying table you will see (with references) that the U.S. Government Printing Office defines noon as 12 a.m. and NIST as 12 p.m. Those together document the dispute. −Woodstone (talk) 19:19, 13 December 2009 (UTC)

Thanks, I already checked that. That is an old version and the errata has been corrected. The latest version, the 30th Ed, identifies it correctly. The Style Manual is not govt statutes or administrative code. It's just a writing guide. Other documentation would be req'd, especially in light of the revision. JackOL31 (talk) 19:26, 13 December 2009 (UTC)

I just double-checked. I see the 30th Ed (2008) indicates:

b. Clock time (see also Time):

4:30 p.m.; half past 4

10 o’clock or 10 p.m. (not 10 o’clock p.m.; 2 p.m. in the afternoon; 10:00 p.m.)

12 p.m. (12 noon)

12 a.m. (12 midnight)

 JackOL31 (talk) 19:34, 13 December 2009 (UTC)

Hmmm, looks like all of your references to the time at midday and at midnight are out of kilter. I spent 32 years in the military and then another 12 in the aviation regulation business and I can tell you that 12 am is midday andd that 12 pm is midnight. Look at it this way: both noon and midnight last for an infinitesimal amount of time. right up to the instant of 12 am is still a morning time and then it trips over into the afternoon. Towards midnight the time is always pm until that picosecond after 12 pm when it becomes a morning time which is always the am.

To do it the other way is silly as a piece of logic. Twelve, midday, is not the start of the afternoon it is the end of the morning. So 12 am is the last instant of the morning, just as 12 pm is the last instant of the after-noon. To get it straight in your mind just think of what that word afternoon means. If you're finding it hard let me tell you that 12 am is noon and after that you have all of the pm (times) hours.

If you don't like my logic try calling your local weather service or aviation service provider, or even the FAA's FSDO representative anyt any major airport.

I'm seriously shocked that the USGPO now says that it is the wrong way about. My copy of of their Style Manual from 1963 has it the way I explain above for the reason I have said. Maybe the 30th Ed of 2008 was edited by someone who is misconceived too? Lin (talk) 05:19, 22 January 2010 (UTC)

Long discussions (now archived) and references have established that 12:00 a.m. is commonly meant to be midnight, so 12:01 a.m. is one minute later to match. You will see this usage on any computer set to 12-hour display. −Woodstone (talk) 09:47, 22 January 2010 (UTC)

The use of "undefined" is not the most appropriate term for the 12-hour cell since 24:00 does not exist in the 12-hour world. This article is from the 12-hour system perspective (left-handed) and right-handed time notation does not exist. As a general rule of thumb for table entries where a cell exists but no value applies to the situation, an entry of "Not applicable" is made. JackOL31 (talk) 01:43, 15 December 2009 (UTC)

This table does not compare general English words. It compares 1-to-1 clock values. The concept of 24:00 does not exist, not applicable to the 12-hr system. My edit is reasonable and valid. Please discuss if there is disagreement. JackOL31 (talk) 12:11, 15 December 2009 (UTC)

Midnight at the end of a day is certainly an existing time that is expressed in English language. Many opening hours or contract durations involve that time. Therefore "not applicable" is not a correct description. There is just not a simple unified short way of writing it.

The statement of usage of a.m./p.m. at 12 o'clock is only meaningful for digital clocks (not analog ones). Mentioning that specifically is useful information in view of the ambiguity.

−Woodstone (talk) 12:52, 15 December 2009 (UTC)

However, here we are not talking about clocks per se, analog or otherwise. We are showing the 1-to-1 relationship between the two systems. The words are added for clarification, but midnight end of day does not exist in the 12-system. In conversation one can say specifically midnight end of day, but it does not translate into a value in the 12-hour system. Why do you not think people will understand "n/a", it is a common enough concept? (I do appreciate the dialog) JackOL31 (talk) 13:09, 15 December 2009 (UTC)

Just as an FYI, I have a analog mantel clock that stops chiming and striking after 9PM. It picks up again at 6AM. I have also seen analog wall clocks that have external AM/PM complications. One in particular has a circular complication above the 6 with a small hand that moves clockwise, the left side marked AM and the right side marked PM. JackOL31 (talk) 13:21, 15 December 2009 (UTC)

I am referring to the first table here. The second table I am replying to in the above section. JackOL31 (talk) 13:39, 15 December 2009 (UTC)

In my understanding "not applicable" implies that the mentioned time does not exist. In my view its expression is merely "undefined" in the 12-hour system. A subtle, but real difference. On your (or any) analog clock at precisely 12 o'clock you cannot determine if the marker is a.m. or p.m., since the indicator will be just on the boundary between them. You can still determine if it's midnight or noon, because there are two such boundaries. On a device that just flips between them even that is not clear at the very instant. −Woodstone (talk) 14:24, 15 December 2009 (UTC)

Yes, the time 24:00 does not exist in the 12-hour system. This is why you cannot put a value in the entry next to the 24:00 entry. It simply does not exist. It is not applicable to the 12-hour system, whether anyone personally believes in a timeframe of 24:00-ness or not. What is important is that the 12-hour system does not believe in (i.e. incorporate) this concept and offers nothing regarding it. Consider the situation where one is writing an article on the 12-hour clock and one has never heard of the 24-hour clock system. Would that person be putting an entry of 24:00 (or some equivalent) in the table? Would that person even write out that particular row? The challenge is to look at this from a "12-hour system" perspective and not through a "24-hour system" pair of glasses. This means one must avoid taking concepts from one system and projecting them into another. No matter how hard you try, the Roman numeral system will never have a 0!

Regarding your comment on the limitations of physical timepieces, I don't see how that plays a part in our discussion but I will comment. If a analog timepiece changes to 12:00, I know at that very same instant the AM/PM indicator has toggled to the other value. The marker moves clockwise, so if it's at the "12 o'clock position" (or 6 o'clock position) I know the time, even if it is on the border. Yes, there are limitations to analog clocks, negligible as they are. However, many of them have character and beauty, and are works of art. Digital clocks will always be functional, sterile and butt ugly. That's why tower clocks are analog (real towers). JackOL31 (talk) 01:59, 16 December 2009 (UTC)

The Introduction section states that there exists/existed a dispute between the US Govt Printing Office and the generally understood standard regarding how 12 o'clock is displayed with respect to AM/PM for "beginning of day" and "noon". A excerpt is cited from the US Govt Printing Office Style Guide (29th Ed) and compared to everywhere else you can find the 12-hr standard listed, including the US GPO Style Guide 30th Ed. First, the GPO Style Guide does not set policy, it guides one in producing standard looking documents. Secondly, it cannot be shown that it is anything more than an error in printing. Errors in printed content do not imply a larger meaning. There is no evidence that the GPO intended to dispute the generally understood AM/PM settings for the respective times. Also, in light of the revision which reverses the entries and does a 180 on the meaning, I recommend any discussion regarding a dispute or the 29th Ed contradiction (Confusion section) be removed in its entirety. The table entry should be updated to reflect the most recent 30th Ed and the values contained therein or be deleted. JackOL31 (talk) 16:42, 19 December 2009 (UTC)

Unfortunately, I feel I must add the following to my previous comments. When I bring up additions, corrections or deletions to content, I expect to make those contributions. I'm happy to discuss significant changes and hopefully come to an agreement, but I would not expect my recommendations to be acted upon by someone else. I am capable of implementing my own recommendations and I would expect that as common courtesy. JackOL31 (talk) 17:55, 19 December 2009 (UTC)

If this last paragraph was aimed at me, I apologize. After I read your previous comments, and reread the article, I had to agree with you. I must confess I was too lazy to first discuss the changes here and implemented them right in the page. −Woodstone (talk) 18:33, 19 December 2009 (UTC)

Well enough, it's a good reminder that none of this is so urgent that we can't discuss it first. Anyway, apology accepted and we'll move on. Since you have not commented on my post previous to the last, I am assuming you're thinking it over. If you agree with me, we'll let it sit for awhile to see if anyone else has any thoughts they'd like to share. Then, assuming no objections, I'll go ahead and make the necessary changes. If you don't agree, we can discuss it some more. JackOL31 (talk) 21:46, 19 December 2009 (UTC)

As per my entry of 2 weeks ago (see above, "The Introduction section states..."), I have deleted the reference to a dispute which was not shown. A Style Manual does not carry any weight regarding govt regulations or policies. The most obvious assumption is that this was clearly an error and not indicative of a dispute between the GPO (charged with maintaing publications) and NIST or any other time organization. The complete reversal of this entry in the next edition is more than not indicative of a correction rather than a power struggle within the GPO organization with a new victor emerging. If one is to claim that the GPO intentionally decided to interpret AM/PM differently than what is the generally accepted historical understanding, one needs more proof than a contradictory entry in a style guide. If this entry is to be taken as proof, then we must also conclude that it becomes p.m. at 12:15 in the afternoon and it becomes a.m. at 12:25 in the wee hours of the morning - since these are the only entries the GPO Style Guide makes with respect to the relationship in the 12-hour system.

12 a.m. (noon); 12:15 p.m. (15 minutes past noon)

12 p.m. (midnight); 12:25 a.m. (25 minutes past midnight)

Please discuss if you feel otherwise. JackOL31 (talk) 14:21, 1 January 2010 (UTC)

Along the same lines, I have modified the table to reflect the current 30th Ed info from the US GPO Style Guide. To cite an older edition which has been corrected is improper. Once again, one must consider the most reasonable and plausible explanation in these situations. If an entry in a book is contradictory to common knowledge without explanation and then reversed to agree with common knowledge in the next updated edition, I believe one must first conclude a correction rather that a disagreement within the publishing organization. The most egregious claim was "Two separate official style documents of the United States government disagree on the correct usage." To me, it appears to be stated in that manner to avoid stating that it was the same style document, with the latter being the most current revision. JackOL31 (talk) 15:03, 1 January 2010 (UTC)

While trying to verify the statements of Lin above I stumbled on the following document from a very official organisation. It contains:

Career Opportunity, U.S. Department of Transportation, Federal Aviation Administration

Announcement Number: AAC-AMH-08-GAV-006-10911; Opening Date: Oct 16, 2009; Closing Date: Sep 30, 2010

Your application must have a status of "Submitted" before 12:00 AM (midnight) Central Time on the Close Date for it to be accepted.

Logically this can only mean that a submission at any time during Sept 30 will be rejected. A 12 AM midnight on a date is surely not after the noon of that day. However I am fairly sure they mean that any submission on Sept 30 is still valid. Furthermore it contradicts Lin's claim about aviation. −Woodstone (talk) 16:46, 22 January 2010 (UTC)

I grew up in Kenya and remember that on New Years eve we waited until 12 pm for the New Year to roll around. I remember being quite amazed to find that in the United States noon was now 12 pm instead of midnight. Metricmike (talk) 01:07, 6 September 2010 (UTC)

It appears that in the original 12 hour time "system" the anti meridiem and post meridiem refer to hours past the hour of noon (the meridiem), therefore 12 noon was neither am nor pm and midnight was both 12 hours anti meridiem and 12 hours post meridiem. Perhaps this is why there is so much confusion. No amount of official US Government documents will clear this up because other countries and other people have a different concept of am and pm. In Kenya the locals count the hours from sunrise to sunset only, if the sun rises at 06:00 that is zero hour, then noon is 6 o'clock and 4 pm is 10 o'clock. I believe this was the case in all ancient societies until the invention of the (church) clock which could run 24 hours a day. Metricmike (talk) 01:20, 6 September 2010 (UTC)

History and use

Modified the last paragraph to include the inner ring values of 00 & 24 for the 12. Improved some of the wording. Also deleted the redlink to Comparison of the 12-hour and 24-hour clocks, which was deleted in October. JackOL31 (talk) 01:52, 19 December 2009 (UTC)

In the "Use by country" subsection, I revised the wording to present a more NPoV. The use of the term "unambiguously" is not necessary. It is sufficent to indicate the alternative terms to a.m./p.m. where it is not used or known. JackOL31 (talk) 03:47, 5 January 2010 (UTC)

The above seemed like a small change, changing wording slightly for NPoV. Otherwise, I would have posted chg in discussion and asked for comment. Once change is made, please discuss if differing view. I don't expect my good faith edits to be backed out. Please discuss why a more neutral PoV is not the proper wording. 173.88.207.233 (talk) 05:24, 5 January 2010 (UTC)

Oops, I did not login above. JackOL31 (talk) 05:27, 5 January 2010 (UTC)

Your anonymous modification made a correct reflection of reality rather inaccurate. Therefore I had no doubt reverting it on sight. Here the explanation:

• In many ... countries the 12-hour clock is commonly used ...
  • sets the reader on the wrong footing; it may be used, but mostly in informal statements only
• In some instances, the terms a.m. and p.m. are not used or known.
  • outside the English speaking countries they are almost never used and often unknown; circumlocution is the only way of disambiguation.

These points were very clearly stated before your change. I do not see any POV in all this. They are statements of fact, not opinion. −Woodstone (talk) 14:15, 5 January 2010 (UTC)

I always try to bear in mind that even anonymous contributors are allowed full privileges when updating. Unless there is vandalism or gross misinformation, there is nothing to lose by starting a discussion and reaching an understanding prior to reversing out someone else's time and effort.

On another note, I can agree with your revisions. I propose the following:

In many European countries and Western countries, the 12-hour clock is commonly used in informal speech with descriptive phrases such as in the morning, in the afternoon, in the evening, and at night.[citation needed] Outside of English speaking countries, the terms a.m. and p.m. are rarely used and often unknown.

Non-neutral wording does not necessarily imply opinion, statement tone and innuendo also play a part. Wikipedia calls it a disinterested tone, I think of it more as a matter-of-fact tone. The earlier changes move toward that tone and also improve the concept flow.

I don't believe I can agree with your circumlocution assertion. I lean more towards - say it once, say it precisely, and say it concisely. JackOL31 (talk) 04:11, 6 January 2010 (UTC)

Can accept proposed new wording. Circumlocution was meant to apply to expressing the abbreviation a.m. by a phrase like "in the morning". In non-English Europe that is practically the only way the 12 hour clock is disambiguated every time it is required. −Woodstone (talk) 04:34, 6 January 2010 (UTC)

Changes made with one small exception, used "seldom" in place of "rarely". Seldom seemed more appropriate. This info still needs a citation though. Regarding your last statement, I perceive things differently than you. One can say 6:30 p.m., 18:30, or 6:30 in the evening. There is no aspect of ambiguity requiring disambiguation. It is flat out unambiguous. The interesting aspect of the 12-hour system is that one could say, for example, "I look forward to seeing you tomorrow at 6:30" and 99 44/100% of the time the correct meaning is still understood. For the other 56/100% of the time, you simply don't abbreviate. I've been saying that since '93. (Eh, that would be 1993 - not 1893, but you already knew that!) JackOL31 (talk) 01:51, 7 January 2010 (UTC)

Features of the 12-hour clock

Made a couple of small improvements/corrections. Changed "which almost all have just 12 hours" to "most of which display only 12 hours". Also, modified the reference to chiming the hour to striking the hour. A clock may chime on the hour, typically 4 times, but it strikes the count of the hour. They are two separate concepts. A few Wiki articles have this wrong, but I will take that up on their respective discussion pages. Removed the overstatement "requiring an understanding of it". First, there is no need for anyone to understand it (other than the clock manufacturer) for a clock to strike three times at 3 o'clock. Secondly, these are the same people who use "in the morning", "in the afternoon", and "in the evening". If you're around a 12-hour striking clock, you're know enough to get by. There needs to be some evidence of people hearing striking clocks and having difficulty understanding them to suggest "a required understanding". Everything requires an understanding in one way or another. JackOL31 (talk) 04:18, 7 January 2010 (UTC)

Section: Criticism and practical problems

This article states that one of the problems with this convention is that "It is not immediately clear on an analogue clock whether a time is a.m. or p.m." Calling 6:00 p.m. "1800" won't solve this problem, either. (The only reason I noticed this is that I've been working on a 24-hour analogue clock. Everybody seems to like it so far except for little kids).

And one more thing: Is it really more complicated to implement in software and digital electronics? How much code does it take to convert 1300 to 0000 to pm? That's like saying it's more difficult to eat a 45 oz steak as opposed to a 40 oz steak. Technically, yea. But no one's gonna notice. —Preceding unsigned comment added by Antigrandiose (talk • contribs) 19:41, 31 March 2010 (UTC)

The use of twelve instead of zero

I recall that the use of 12 instead of 0 in clocks was attributed to the non-existence of the number 0 until the 10th century, though I can't seem to find a source to evidence this, does anyone here know more about this? —Preceding unsigned comment added by 115.64.132.151 (talk) 14:03, 10 August 2010 (UTC)

Is it exactly 24 hrs between midnight to midnight, every day of the year or does it vary and averages to 24 hrs ?

It just came to my mind. This may be vague, and may not be a question though, in the universal context is our 24 hrs a 24 hrs exactly the same everyday from midnight to midnight. or does it vary each day and averages to 24 hrs every year i.e on full revolution. Chandrakantpushkar (talk) 09:22, 21 September 2010 (UTC)

It depends on what you mean. In the sense of 12-hour clock every day is precisely 86400 seconds, except once in many months, when a leap second is added, and that day is 86401 seconds. However if you mean the time between the Sun being at its highest point on successive days, it varies quite a bit, somewhere in the order of plus or minus 20 seconds. Over months it adds up to plus or minus 15 minutes. See for a detailed explanation Equation of time. −Woodstone (talk) 16:15, 21 September 2010 (UTC)

POV

Original edit summary [1] "It's been my experience traveling the globe that everyone uses the 24 hour system with the exception of the U.S. Look at the website for airlines in any country to see what time system is used."

As you can see "My experience" is POV (where's the citation?), and airlines typically ALWAYS use the 24 hour clock around the world, just as trains do, and other forms of public transport! That doesn't say anything about what people use on a day to day basis, or even other businesses apart from transportation. Strange how the edit was by "MetricMike" who "wish[es] the US would get on with the conversion to the much simpler and more rational System International". Obviously biased editing. 91.85.177.45 (talk) 07:01, 26 September 2010 (UTC)

Let me 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 but I will try my best so 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 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 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) 12:09, 29 October 2010 (UTC)

Updates and active discussion [[2]].