# When did we go from 12 midnight and 12 noon to 12 am and 12 pm? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [November 11, 2014, 11:10am UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329 "2014-11-11T11:10:56Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [November 11, 2014, 4:58pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/21 "2014-11-11T16:58:57Z")
Oh, NM. I see this was already proposed. Hey, if it helps, consider this: every time you’re aware of it “being” 12:00 (either one), is at least a moment after the strict instant of the meridiem, right? Thus, you have entered the next “half” of time. ---
**Author:** ![Suburban\_Plankton](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/suburban_plankton/32/219_2.png) [@Suburban\_Plankton](https://boards.straightdope.com/u/Suburban_Plankton)\ **Post date:** [November 11, 2014, 5:07pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/22 "2014-11-11T17:07:14Z")
> [@Telemark](#): > > I’m 51 and have the same experience. I don’t believe this is a terribly new phenomenon. I’m “only” 47, and it’s always been the same for me as well. That said, there have always been a great many people who either don’t ‘get it’ or just plain refuse to follow convention. I’d support everyone moving to ‘military time’ and removing any possible ambiguity… ---
**Author:** ![Dr.Drake](https://avatars.discourse-cdn.com/v4/letter/d/ad7895/32.png) [@Dr.Drake](https://boards.straightdope.com/u/Dr.Drake)\ **Post date:** [November 11, 2014, 5:08pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/23 "2014-11-11T17:08:44Z")
> [@Peremensoe](#): > > Hey, if it helps, consider this: every time you’re aware of it “being” 12:00 (either one), is at least a moment after the strict instant of the meridiem, right? Thus, you have entered the next “half” of time. That’s the mnemonic I use, but it will always be counter-intuitive, because we simply don’t count 12-1-2-3-4-5-6-7-8-9-10-11 in ordinary circumstances, so it’s hard to remember that 0 ≤ 12 \< 1. Edit: “noon” and “midnight,” as words (and thus less math-y) are helpful ways to make that 0=12 transition to the next cycle, reinfornced by the useful literal meanings of “a.m.” and “p.m.” ---
**Author:** ![doreen](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@doreen](https://boards.straightdope.com/u/doreen)\ **Post date:** [November 11, 2014, 5:24pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/24 "2014-11-11T17:24:25Z")
> [@RTFirefly](#): > > It’s the use of 12 pm and 12 am instead of noon and midnight in _human-to-human communication_ I’m talking about here. I have actually never _heard_ 12 am or 12 pm in conversation. It’s always noon or midnight in conversation ( although that does leave the question of what’s meant by “midnight Tuesday”) I’ve seen it in writing, yes, but I’ve seen it in writing for as long as I can remember - it’s not something new. Although I have noticed that a lot of bills etc now say "payment is due by 11:59 pm on 12/1 " . I assume this is to avoid any misunderstanding of which 12 am or midnight is being referred to if those times were used. Oh and the water bill might not be a screw-up. I’ve had bills that said payment must be received by some specified time other than midnight ( specifically 9am, 3pm and 5pm). It could be they really want the payment at noon- or it could just be to avoid “which midnight is the midnight of 12/1” issue. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [November 11, 2014, 5:51pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/25 "2014-11-11T17:51:12Z")
> [@Ethilrist](#): > > It annoys me because 12 Noon is neither ante meridiem nor post meridiem; it _is_ the meridiem and occurs exactly when it intends to be, which is noon, Mr. Frodo. If it makes you feel better, 12 noon is a specific point in time, and you’re practically never going to be exactly on that point. As long as you’ve passed it by even a fraction of a second, it’s “post meridiem.” ETA: I see **Peremensoe** has already made this point. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [November 11, 2014, 5:51pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/26 "2014-11-11T17:51:39Z")
It started with the popularity of digital display clocks in the 1970’s (+/- a decade?) that used panels to show the numbers like [this](http://flashscreensaver.com/2010/08/01/fliqlo-flip-style-clock/fliglo/). There was no feasible way to show the instant of midnight or of noon, so the “AM” or “PM” went along with what was correct for the split second following those instants. ---
**Author:** ![Dr.Drake](https://avatars.discourse-cdn.com/v4/letter/d/ad7895/32.png) [@Dr.Drake](https://boards.straightdope.com/u/Dr.Drake)\ **Post date:** [November 11, 2014, 5:54pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/27 "2014-11-11T17:54:01Z")
> [@Thudlow\_Boink](#): > > If it makes you feel better, 12 noon is a specific point in time, and you’re practically never going to be exactly on that point. “Practically never!” I have been exactly on that point once a day, every day, for decades. ---
**Author:** ![fjs1fs](https://avatars.discourse-cdn.com/v4/letter/f/9e8a1a/32.png) [@fjs1fs](https://boards.straightdope.com/u/fjs1fs)\ **Post date:** [November 11, 2014, 5:56pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/28 "2014-11-11T17:56:07Z")
> [@RTFirefly](#): > > Digital clocks have been common since, what, the early 1980s? And automated systems that needed to keep time accurately have been around even longer. > > But, just as one for-instance, my water bill says the check has to be received by 12 pm on such-and-such a date to avoid the late fee. (I think they meant am, since nobody makes noon the line of demarcation for such things, but this just goes to show that even the county is screwed up by this usage.) > > It’s the use of 12 pm and 12 am instead of noon and midnight in _human-to-human communication_ I’m talking about here. I’m so glad to see someone make this point: I hate it when people say “12 am” or “12 pm.” Just say noon or midnight. My other pet peeve is the word bi-monthly. It’s amazing that [dictionary.com](http://dictionary.com) (and probably many other dictionaries) have BOTH of these definitions: adjective 1. occurring every two months. 2. occurring twice a month; semimonthly. That’s why I never use the words “bi-monthly” or semimonthly. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [November 11, 2014, 5:57pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/29 "2014-11-11T17:57:13Z")
> [@Thudlow\_Boink](#): > > If it makes you feel better, 12 noon is… REDUNDANT, that’s what it is. :mad: ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [November 11, 2014, 6:03pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/30 "2014-11-11T18:03:51Z")
> [@Thudlow\_Boink](#): > > If it makes you feel better, 12 noon is… > [@Ethilrist](#): > > REDUNDANT, that’s what it is. :mad: Not if one cares to distinguish between 12 noon and 12 midnight. ---
**Author:** ![doreen](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@doreen](https://boards.straightdope.com/u/doreen)\ **Post date:** [November 11, 2014, 6:21pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/31 "2014-11-11T18:21:13Z")
> [@Gary\_T](#): > > Not if one cares to distinguish between 12 noon and 12 midnight. Still redundant- noon or midnight without the 12 distinguishes just as well. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [November 11, 2014, 6:21pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/32 "2014-11-11T18:21:22Z")
> [@Gary\_T](#): > > Not if one cares to distinguish between 12 noon and 12 midnight. Why do you need the “12”? To distinguish between 12 noon and 9 noon? ---
**Author:** ![Tim\_R.Mortiss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim_r.mortiss/32/142_2.png) [@Tim\_R.Mortiss](https://boards.straightdope.com/u/Tim_R.Mortiss)\ **Post date:** [November 11, 2014, 6:35pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/33 "2014-11-11T18:35:22Z")
I always thought it made more sense for noon to be 12 am, because WTF should 12 \*pm \*follow 11 _am_? The digital clock issue makes sense as an excuse, but it strikes me as playing fast and loose with the space-time continuum and we’ve all seen what that can lead to. ---
**Author:** ![Dr.Drake](https://avatars.discourse-cdn.com/v4/letter/d/ad7895/32.png) [@Dr.Drake](https://boards.straightdope.com/u/Dr.Drake)\ **Post date:** [November 11, 2014, 6:39pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/34 "2014-11-11T18:39:13Z")
I blame Roman inclusive counting. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [November 11, 2014, 6:42pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/35 "2014-11-11T18:42:32Z")
> [@Tim\_R.Mortiss](#): > > I always thought it made more sense for noon to be 12 am, because WTF should 12 \*pm \*follow 11 _am_? The digital clock issue makes sense as an excuse, but it strikes me as playing fast and loose with the space-time continuum and we’ve all seen what that can lead to. The problem is that what we call “12 o’clock” should really be called “0 o’clock.” ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [November 11, 2014, 7:20pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/36 "2014-11-11T19:20:08Z")
But doesn’t “o[f the]clock” literally refer to a clock face? Where there is no zero. > [@ZenBeam](#): > > Why do you need the “12”? To distinguish between 12 noon and 9 noon? For me, it would be to distinguish 12:00 noon, the more-or-less precise moment, from “noon[time],” the span. Just as I’d use 3:30 AM in some contexts, “wee hours” in others. ---
**Author:** ![Abner\_Ravenwood](https://avatars.discourse-cdn.com/v4/letter/a/c4cdca/32.png) [@Abner\_Ravenwood](https://boards.straightdope.com/u/Abner_Ravenwood)\ **Post date:** [November 11, 2014, 7:51pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/37 "2014-11-11T19:51:19Z")
If we’re getting overly pedantic over this matter, shouldn’t we be using words other than midnight and noon for 12 am and 12 pm? Midnight is rarely if ever midway through sunset and sunrise, and noon comes from the Latin ‘nona hora,’ signifying the ninth hour of the day. ---
**Author:** ![somepumpkin](https://avatars.discourse-cdn.com/v4/letter/s/7feea3/32.png) [@somepumpkin](https://boards.straightdope.com/u/somepumpkin)\ **Post date:** [November 11, 2014, 7:52pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/38 "2014-11-11T19:52:53Z")
> [@Ethilrist](#): > > :dubious: > > 12:00 PM = 8 characters. > Noon = 4 characters. > > 12:00 AM = 8 characters. > Midnight = 8 characters. Ok… but: > [@RTFirefly](#): > > When did we go from 12 midnight and 12 noon to 12 am and 12 pm? 12 midnight = 10 12 am = 4 12 noon = 6 12 pm = 4 That is all. 🙂 ---
**Author:** ![Steophan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steophan/32/9595_2.png) [@Steophan](https://boards.straightdope.com/u/Steophan)\ **Post date:** [November 11, 2014, 10:49pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/39 "2014-11-11T22:49:38Z")
> [@ZenBeam](#): > > Why do you need the “12”? To distinguish between 12 noon and 9 noon? Given it originally meant the 9th hour, or 3pm, then yeah, possibly. ---
**Author:** ![RTFirefly](https://avatars.discourse-cdn.com/v4/letter/r/c77e96/32.png) [@RTFirefly](https://boards.straightdope.com/u/RTFirefly)\ **Post date:** [November 11, 2014, 11:18pm UTC](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329/40 "2014-11-11T23:18:56Z")
> [@doreen](#): > > I have actually never _heard_ 12 am or 12 pm in conversation. Not in conversation, but in letters from companies, emails from HR or TPTB at work, and so forth. > [@Dr.Drake](#): > > “Practically never!” I have been exactly on that point once a day, every day, for decades. Tru dat, but OTOH it’s taken up exactly 0% of your life. 🙂 [Previous page](https://boards.straightdope.com/t/when-did-we-go-from-12-midnight-and-12-noon-to-12-am-and-12-pm/704329.md?page=1)