I've been silently ruminating for several days now. Admittedly, I hesitated to say anything because the upvotes my answer accrued finally permitted me to reach that mythical 10k milestone. But, after careful consideration, I believe that the OP posted their question on the wrong Stack Exchange site.

It's patently clear that the OP wanted a technical, not a language, explanation.

Every new answer offers the same computer engineer's mindset; the same concepts, point out the same discrepancies in the 12-hour clock, and completely fail to focus on the English language aspect. Undeniably, no one topped tchrist's splendid opening paragraph for its breadth and deftness.

What you see with “11 ᴀᴍ + 1 hour == 12:00 ᴘᴍ” is largely an artifact of the way we keep time with a zero-based system on computers per ISO 8601, and what happens when you map a zero-based 24-hour time like 00:00:00.00000 into a 12-hour ᴀᴍ/ᴘᴍ time, which is one-based.

But as admirable as tchrist's answer is, as well-written as it is, was the Original Post really a language poblem? How helpful are its answers to learners? As an example, I offer another snippet of @tchrist's answer

Alas this confusion of ordinals and cardinals starts young, back when we first teach our toddlers how to count items. When you number items using ordinal numbers, you have a first item, then a second item, then a third item. We teach our toddlers to start with one, two, three instead of with zero, one, two. The concept of zero is more complicated than a two-year-old needs. If you with perfect accuracy tell them they’re in their third year instead of in their second year when they’re “two years old”, they won’t understand you. That certainly won’t make sense to them then, and for some it may never make sense.

That paragraph is introducing the reasons why midday and midnight are historically represented as 12:00. Although, I'd argue, if you take away a two-year old's chocolate cookie and tell them they have zero cookies, the concept of "zero" becomes crystal clear. But I digress.

The question attracted a slew of other "technical" answers. For example,

@CJ Dennis's answer

In mathematics, a number range can be represented as:

(0-12) zero to twelve, not inclusive
[0-12] zero to twelve, inclusive
(0-12] zero not inclusive to twelve inclusive
[0-12) zero inclusive to twelve not inclusive

The parentheses ( & ) indicate that the adjacent number is not inclusive, i.e. that it is excluded from the range. The brackets [ & ] indicate that the adjacent number is inclusive, i.e. that it is included in the range.

here's a snippet of @kwah's answer (bolding not mine)

Given this pattern of all other times after noon and before 1PM having the PM suffix it is, therefore, common to (incorrectly) assume that 12:00 noon also needs to be labelled PM but, as shown above, this is not the case.

and @Rob's answer

Solar time is directly derived from the Sun's position, by counting one hour of time every 15° of hour angle as Earth is rotating around its axis in 24 hours, which gives 360°/24 h = 15°/hour. So, 15 * 12 = 180, thus half a circle measures 12 hours.

the Romans got mentioned a couple of times, for instance in @aij's answer

You have knowledge that the Babylonians and Romans did not have. They did not know of this strange number 0.

12 is congruent to 0 (mod 12), so XII is the number the Romans had that made the most sense between XI and I.

@David K's answer

But place-value systems typically allow any of their digits to be zero. In binary, as you count up each digit changes from 0 to 1 and then to 0 again; in decimal it goes from 0 to 1 and so forth up to 9 and then to 0.

When telling time, the minutes and seconds also follow this rule: after 59 we have 0. But the hour is an exception: the next hour after 12 is 1. Worse still, the change in the date doesn't occur then, but occurs one hour earlier, between 11:59 pm (one minute before midnight) on one day and one minute after midnight on the next day.

The ELL help centre says questions should be about the following (emphasis mine)

  • Word choice, usage, and meaning
  • Grammar
  • Dialect differences
  • Spelling and punctuation
  • Pronunciation and accents
  • Other practical problems you encounter or face while learning English

To sum up, and crystallize my hamletic dilemma, is the OP's question
If Why is 11 am + 1 hour == 12:00 pm? off-topic, what should be done?

  • Should Yuki Inoue's question be migrated, maybe to SE Mathematics, SE Cross Validated, or SE Computer Science?
  • Should it be frozen, i.e. locked?
  • Should it be turned into a Community Wiki post?
  • Should it be closed?
  • Should it be left alone because it generated high-quality answers?
  • 3
    While I have the same doubts about whether it was really an ELL question, I wonder what would be the value of doing anything to it other than the existing protection. The community could have voted to close it, but it didn't receive one close vote. It and its answers have good scores, so the community was definitely interested in it. The accepted answer has a resounding 260+/3- votes and there are several other 10+ scored answers. It's not a math question, or a computer science question. If we had a chronometry SE where it was an obvious fit, I would migrate it in a heartbeat.
    – ColleenV
    Jan 16, 2018 at 22:27
  • 1
    @ColleenV Of course, no one was going to vote for its closure, why would they? Initially, it looked like a learner struggling to understand why PM was used. I far and away underestimated the real scope of his question, until I saw it had hit HNQ for five days in a row and attracted a swarm of comments about "zero" "digital clocks" and "binary". Hello???
    – Mari-Lou A
    Jan 16, 2018 at 22:32
  • 3
    Why would the answers change whether a question was on-topic or not? Folks could vote to close it right now if they wanted to - there's no time limit (there is on migrations however). I'm on the fence. I'm still looking for a good reason to do anything other than let it be and can't think of one.
    – ColleenV
    Jan 16, 2018 at 22:34
  • @ColleenV interesting problem though, isn't it? I've been peering over the fence for days :) Wondering why nobody mentioned anything.
    – Mari-Lou A
    Jan 16, 2018 at 22:44
  • I think everyone bit their tongue because it turned out to be a really interesting question and it has great answers of all levels. No-one wanted to lose all of that good stuff just because it turns out there are some historical and other non-language parts lurking just below the surface. Your answer does a good job of tackling the language question, so I think a learner wouldn't walk away empty-handed if they found this question on ELL. More fluent learners would benefit from all of the positively scored answers, if only to read well-written English about an interesting topic.
    – ColleenV
    Jan 16, 2018 at 23:01
  • Also, not to brag too much, but check out some of the other search engine results for the same question: Quora/Yahoo /Word Reference Forums The Internet needed us to tackle this question :)
    – ColleenV
    Jan 16, 2018 at 23:06
  • I wish all our bad questions were as good this clock question. By the way, congrats on earning your way to the 10K level.
    – J.R. Mod
    Jan 17, 2018 at 15:50
  • 2
    @J.R. To be clear, I never said the question was "bad" just "off-topic" but thanks anyway for the congrats.
    – Mari-Lou A
    Jan 17, 2018 at 19:04
  • @Mari-Lou - To be clear, my remark was meant to rather tongue-in-cheek, and I used the word "bad" although I really meant "potentially off-topic." I think you've articulated your main points quite nicely here, and it was evident that you, too, admire the question, but simply wondered if it was asked in the right place.
    – J.R. Mod
    Jan 17, 2018 at 19:32
  • 2
    Just a lurker here... personally, I see the linked question as a history of time, but related to the language (just like "why B.C. then A.D."). I can't see that question on-topic on Math.SE, Stats.SE, or even CS.SE. Perhaps, more appropriate in History (they have time-keeping tag)... or any other sites that accept the history aspect of a language?
    – Andrew T.
    Jan 18, 2018 at 4:03
  • @AndrewT. you have found the ideal site where the question should be migrated. SE History just never occurred to me, but there are questions about midnight and mid night history.stackexchange.com/questions/30249/… and here history.stackexchange.com/questions/38970/…
    – Mari-Lou A
    Jan 18, 2018 at 10:40
  • Adieu to my 10K ¯_(ツ)_/¯
    – Mari-Lou A
    Jan 18, 2018 at 10:43
  • 5
    I don't know why we would migrate it when it got great answers here already, and it wasn't considered off-topic here when it was asked. The reason you migrate is so that the question gets a good answer, not so we properly categorize it... Google doesn't care which SE site the question lives on :)
    – ColleenV
    Jan 18, 2018 at 21:49
  • Would an historical lock be appropriate here? As I understand it, the question would stay answered and visible but with an addendum that it might no longer be considered "on-topic" (as a guide for similar, future questions).
    – Gossar
    Jan 22, 2018 at 21:17
  • 1
    @kiamlaluno I would be happy if we had more users searching for questions to pattern their question after instead of asking questions that are off-topic because there's no context and no explanation of what is already known. Regardless, if the community wants it locked, I'm here to serve. Let's post an answer suggesting a historical lock and if it gets support, I will make it happen.
    – ColleenV
    Jan 28, 2018 at 12:24


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