We count the hours from 1 to 12, and then we start over. That change occurs at noon and midnight. But I’m wondering why we keep on the 1 through 12 numbering when we’re past noon, or when we’re past midnight. It seems that the a.m. hours and the p.m. hours should contain the hours of one o’clock through to 12:59. At that point, when we’re out of numbers and we’re about to start over, would be a good point to start p.m or a.m. Why don’t the numbers coincide with the events we refer to as ante and post meridian? The only time that it seems moderately accurate is when we’re on daylight savings time. Then, when the sun is highest in the sky, the numbering shifts from 12 back to 1. That seems like it should be the default. How did we wind up with the system off by one hour (in my way of thinking)?
PM means after noon - it doesn’t mean after (one hour after) noon.
p.m. refers to the fact that the sun is past the meridian where we are: post meridian. But even if we take what you say as truth, why should noon be 12:00? Why not 1:00? That’s my question.
Think of 12:30 as 00:30, which is what it really is, and you’ll understand it.
And 1:00 P.M. as 1300.
Yes, it functions that way, but it’s not that way. It’s, in fact, 12:30, not zero thirty, because we don’t use a zero hour. Since we’re using the 1-12 numbering system, the noon changeover should coincide with the numerical changeover.
To fly in the face of all the math geeks who got all pissy about calling 1/1/2000 the beginning of the millenium because you don’t start a numbering system with 0, you start with 1.
The comparison with the year numbering system, which I thought about before posting my question, is not direct enough. We’re talking about a circular system in which every minute is part of some hourly designation. We don’t have any beginning. We don’t start at zero and then move along until we’ve completed an hour, as we do with years. When morning changes to afternoon, when night changes to morning, the numbering system should accordingly start over. And my question is why doesn’t it? How did this happen?
I’m not a horologist, but my guess would be:
1AM (and PM) is one hour past the divider (midday or midnight). If you started at 1, than 1 hour past the dividing line would be 2 which would be a bit confusing.
It would work though, so it’s probably just convention.
Maybe not. When we were in the second hour past midday or midnight, we’d be in the 2’s. Second hour would be a term we might even use to refer to the time in general.
Then, I suggest you start a movement to change the way clocks are labeled. You can team up with Dvorak and the Metric crowd.
Maybe Timecube would be interested.
In military time, it is zero thirty.
Exactly what I was going to say.
Similarly, an hour and thirty minutes past noon is 1:30 PM.
Yes, but then how do you deal with the minutes? Suppose we were in the second hour, and we were in the fifth minute of that hour. I guess you’d want to call that 2:05. And if we were in the last minute (i.e., the sixtieth minute) of that hour, we’d call it 2:60.
What you are suggesting is logical. But people have found it simpler to mark how many hours have passed, rather than the hour which we are in.
Hell, I’ve always thought that the day should officially start at 6am, not midnight, coinciding (roughly) with local dawn.
Not really. You start a continuous measure at 0. A train leaves city C at S miles/hour and you count the miles as 0.0, 0.1, 0.2 etc.
You count discrete quantities begining at 0 also but you start counting at one. If I start giving you oranges you have 0, then 1, then 2 etc. Except that you start counting as I give you the first one and skip the zero.
The problem lies when we count continuous amounts as discrete numbers. For example “I am in my first year of college”, “in the second century AD”, etc. It is OK so long as you understand what is being meant but it can lead to misunderstanding. A person in his first year of college has not completed any years of college. Something that happened in the first hour of a show happened before one hour of show had been completed. A baby who is six months old is in its first year of life but it is not one year old.
Saying 12:30 rather than 0:30 is just easier but everybody literate understands the count starts at 0 even if we call it 12. Maybe the question should be why do people prefer to call it 12:05 rather than the more correct 0:05.
I don’t think that’s the question. I think it should be as I framed it - why doesn’t noon happen at 1 o’clock, when the change in numbering happens? When we go from one day to the next, the numbering system should coincide, and we should go from counting in the 12’s to counting in the 1’s. When the new day starts, the numbering system should start over.
'Cause it doesn’t, and nobody wants to change it. It’s not as if there is a rational justification for it being the way it is (although I do like it better than your way, personally). None of our time measurements make sense: 60 (?) seconds to a minute, 60 minutes to an hour (at least that’s consistent), 24 hours to a day (?!), 365 days to a year (?!!), except every four years, when it is 366 (!!!), except every hundred years when it isn’t (!!!111), except every four hundred years when it is (!!!11one!!). To ask why this isn’t consistent is a bit silly. 
Valete,
Vox Imperatoris
That makes no sense. The change does not happen at 1, it happens at 12/0. The origin is at 0 not at 1.
The question posed has nothing to do with leap years, but since you asked - a “day” is the time it takes the earth to make one revolution on its axis. A “year” is the time that it takes the Earth to revolve once around the Sun. It happens that it’s just about 365.25 days. How would you define a year, given those numbers? The current system works very well, and makes perfect sense.
Yes, but it’s only 365.25 days because of the arbitrary length of the second, minute, and hour (mainly the second, since it’s just a completely arbitrary length of time that was settled on long ago, although I realize that they have precise SI ways of defining what that arbitrary length is). And I was just making the point that the rest of the time measurement system is completely arbitrary, even where it does make sense to some degree, so there’s no reason to expect the placement of the noon hour to coincide with what makes the most sense in the OP’s mind.
Valete,
Vox Imperatoris