The reason 12 is at the top of the clock is because on the original sundial their weren't numbers and they were technically 24 hour long clocks. The counting of hours and switching between AM to PM happened when the sun dial aligned with the tippy top of the dial. If you've ever used a sun dial the easiest time to read it is high noon. So that's where we started the counting. When the dial was 1/24 through the day/night that was 1 hour. So consequently cause again easiest time to read a sun dial is at high noon. It became 1 pm. Each 24th of the day elapsed until we got back around again. But we invented space saving 12 hour clocks and obviously you can't go after twelve straight to one so it became 12:01, 12:02, etc because again that was what was easiest. Tl;dr- we don't start at one because counting from high noon one denotes an hour already having elapsed. We count with 12:01, 02, etc because we had to get to one somehow once we invented the space saving 12 hour clock. Original clocks were 24 hours. Answer from redpenrevolution on reddit.com
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Reddit
reddit.com › r/explainlikeimfive › eli5: 12am is midnight?
r/explainlikeimfive on Reddit: ELI5: 12am is midnight?
December 24, 2018 -

I feel like there's weird maths thing that makes this all make sense but i can't wrap my head around it.

Why is 12 am midnight?

I feel like that makes it really weird because it means that the am's go from 12am to 1 am to 2 am, etc and like shouldn't it start at 1 and go to 12? Same thing with the pm's like it goes from 11pm then 12am? Shouldn't it be 11pm then 12pm??

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Reddit
reddit.com › r/explainlikeimfive › eli5: why is 12 am midnight and 12 pm midday, when 11 am is 1 hour before midday, and 11 pm is 1 hour before midnight?
r/explainlikeimfive on Reddit: ELI5: Why is 12 AM midnight and 12 PM midday, when 11 AM is 1 hour before midday, and 11 PM is 1 hour before midnight?
August 28, 2017 -

I did some research, and AM means Ante Meridiem (latin for before noon) and PM means Post Meridiem (after noon). Which makes sense for the most part, because 4 AM means the 4th hour in Ante Meridiem, and 8 PM means the 8th hour in Post Meridiem, etc.. It follows a chronological order from 1AM to 11AM, but then at noon it swaps to 12PM, then 1PM to 11 PM, then it swaps to 12 AM again. It's strange, because if you follow the logic of the other hours, 12 PM should mean the 12th hour in Post Meridiem, when it's really the first hour in Post Meridiem. 12 PM sounds like it should be 12 hours after noon, when in reality it is noon.

Why is this the case? It seems counter-intuitive, especially because I grew up with a 24-hour system in Denmark. We just say 19 o'clock when it's 7 PM.

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Reddit
reddit.com › r/explainlikeimfive › eli5: why is midday usually represented as 12pm rather than 12am?
r/explainlikeimfive on Reddit: ELI5: Why is midday usually represented as 12pm rather than 12am?
January 3, 2026 - Midnight (or 12am) is quite obviously before midday, whilst almost the entire minute of 12:00 is after the midday. Edit: ante != anno, had anno 1800 on the brain... ... Ante meridiem and post meridiem!
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Reddit
reddit.com › r/englishlearning › 12.00am means midnight?
12.00am means midnight? : r/EnglishLearning
March 20, 2025 - However: AM means ante meridiem ("before midday" in Latin) and PM means post meridiem ("after midday"). 12:00 of course is midday, so it doesn't really make sense for it to be AM or PM; however, as soon as we're past 12:00 (for example, 12:01) we are after midday, or "post meridiem" (PM).
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Reddit
reddit.com › r/showerthoughts › as midnight is 12 a.m., midnight friday is actually friday morning and not friday night.
r/Showerthoughts on Reddit: As midnight is 12 a.m., midnight Friday is actually Friday morning and not Friday night.
July 21, 2023 - Midnight is not 12am. Midnight and noon are neither am nor pm. That's why we have military time. 0000 is the midnight at the start of a given day, and 2400 is the midnight at the end of a given day.
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Reddit
reddit.com › r/askreddit › when is 'midnight'? is it 12am the referenced day or the next day? does 'midnight, tuesday' reference 12am wednesday or 12am tuesday?
r/AskReddit on Reddit: When is 'midnight'? Is it 12am the referenced day or the next day? Does 'midnight, Tuesday' reference 12am Wednesday or 12am Tuesday?
November 2, 2018 - Midnight is twelve a.m. ... Of which day? There was a huge debate on fb I'm trying to settle, in my own head. I've always known it to be 12am the next day. (so, the night of the referenced day) but apparently there are people who think it means ...
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Reddit
reddit.com › r/grammar › what day is midnight?
r/grammar on Reddit: What day is midnight?
April 4, 2023 -

When someone says “I have a flight to catch on Monday at midnight.” do they mean the 12am between Sunday and Monday, or the 12am between Monday and Tuesday?

I think it depends on what time does the day actually start. I believe it’s 12:00am. So I’m thinking “on Monday at midnight” is the beginning of the day on Monday right after Sunday. But it sounds weird because the word “midnight” seems to have a very late connotation to it rather than actually being early. I’m not sure, but I would think that’s why actual flight times never fall on 12:00 on the dot to avoid confusion.

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Reddit
reddit.com › r/questions › how is midnight 12am?
r/questions on Reddit: How is midnight 12am?
March 25, 2025 -

so if 12:00 anything is midnight then the minute after is 12:01 but how could that be?! pretend it’s day 0 so if you wanted to be old timey you’d say it is the first minute of the twelfth hour ante meridian. but how could that be?

it is the 1st minute of day 1 not the last 59minutes of day 0. after midnight a new day starts (at least in christian tradition, I think hebrews do it differently).

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Reddit
reddit.com › r/changemyview › cmv: it would make more sense for 12 pm to be midnight and 12 am to be noon
r/changemyview on Reddit: CMV: It would make more sense for 12 PM to be midnight and 12 AM to be noon
June 25, 2023 -

Okay so first of all, I'm not from the US or UK, so I never used PM in my day to day life. I also believe that a 24 hour system is far superior to the AM PM system, so that isn't going to change my view. I also do not think changing the system this way now makes sense, as it would probably take too much effort.

What made me make this post is a viral Twitter image that made fun of people for not knowing which of four options are closest to midnight: 11:55 AM, 12:06 AM, 11:50 AM, 12:03 AM. The correct answer is D, but it confused a lot of people, and I can fully understand why.

My arguement for why it would make more sense to switch the two is that currently the morning times go: 12 1 2 3... 9, 10, 11. And then it switches to evening and once again starts with 12 and then 1. It would make a lot more sense to have it be 1 AM - 12 AM and then 1 PM - 12 PM. The only reasonable arguement I can see against this is that 12:30 PM would be in the next day so to speak, so it would make more sense to call ot AM. But then call it 0:30 AM to avoid the confusion of starting over. Is this just some ancient holdover from a numbering system that didn't have 0?

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Reddit
reddit.com › r/answers › is midnight 12am or 12pm?
r/answers on Reddit: Is midnight 12am or 12pm?
March 15, 2018 - It's AM. PM is noon. Reply · reply · cruddy_mccrudderson · • · 12am hence mid-night ... middle of the night. Noon, or 12pm is also referred to as midday in some regions · Reply · reply · Cruddlington · • · I think of it as 12 past ...