# Help me with American time notation **URL:** \ **Category:** Factual Questions\ **Created:** [November 4, 2003, 7:27am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307 "2003-11-04T07:27:38Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [November 4, 2003, 7:27am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/1 "2003-11-04T07:27:38Z")
Simple question here. Does 12am mean midnight or noon? If it means midnight, does Saturday 12am mean the midnight between Friday and Saturday or the midnight between Saturday and Sunday? ---
**Author:** ![Reepicheep](https://avatars.discourse-cdn.com/v4/letter/r/ed655f/32.png) [@Reepicheep](https://boards.straightdope.com/u/Reepicheep)\ **Post date:** [November 4, 2003, 7:39am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/2 "2003-11-04T07:39:34Z")
12am means midnight. 12am Saturday means midnight between Friday and Saturday. ---
**Author:** ![racinchikki](https://avatars.discourse-cdn.com/v4/letter/r/eada6e/32.png) [@racinchikki](https://boards.straightdope.com/u/racinchikki)\ **Post date:** [November 4, 2003, 7:42am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/3 "2003-11-04T07:42:14Z")
12am means midnight; 12pm means noon. Exactly at midnight or noon this makes no sense, but shortly thereafter it kinda does - 12:01 pm is after noon therefore pm. Saturday 12am means the midnight between Friday and Saturday - at least that’s how I’d use it. ---
**Author:** ![ccwaterback](https://avatars.discourse-cdn.com/v4/letter/c/df705f/32.png) [@ccwaterback](https://boards.straightdope.com/u/ccwaterback)\ **Post date:** [November 4, 2003, 8:26am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/4 "2003-11-04T08:26:57Z")
At 12AM the day changes from Friday to Saturday. So, 12AM “belongs” to Saturday. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [November 4, 2003, 10:29am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/5 "2003-11-04T10:29:40Z")
Why is this an American convention? Sure, I know that a lot of the world uses 24 hour clocks for official schedules and stuff, but the normal people usually use 12 hour am and pm designations. What’s unique about the North American way of am/pm? ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [November 4, 2003, 10:37am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/6 "2003-11-04T10:37:09Z")
> [@](#): > > \*Originally posted by Balthisar \* > \*\*Why is this an American convention? Sure, I know that a lot of the world uses 24 hour clocks for official schedules and stuff, but the normal people usually use 12 hour am and pm designations. What’s unique about the North American way of am/pm? \*\* I dunno. It’s not the way we Swedes do it, and I needed the information to decode an American webpage, so I thought it best to specify American time notation. They probably use the same notation in Australia for example, but I don’t _know_ that. [This thread](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=150850) indicates that your assumption about time notation in non-American countries is a bit off. ---
**Author:** ![Futile\_Gesture](https://avatars.discourse-cdn.com/v4/letter/f/f05b48/32.png) [@Futile\_Gesture](https://boards.straightdope.com/u/Futile_Gesture)\ **Post date:** [November 4, 2003, 10:40am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/7 "2003-11-04T10:40:17Z")
It isn’t American as far as I’m aware. 12am means midnight the world over, so I’m not sure what the OP is on about. ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [November 4, 2003, 10:53am UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/8 "2003-11-04T10:53:55Z")
> [@](#): > > \*Originally posted by Futile Gesture \* > \*\*It isn’t American as far as I’m aware. 12am means midnight the world over, so I’m not sure what the OP is on about. \*\* As I just said, this isn’t true. The notation “am” doesn’t exist in Sweden, for example. In fact, I’ve never seen it outside English-speaking countries. ---
**Author:** ![Thin\_Ice](https://avatars.discourse-cdn.com/v4/letter/t/aeb1de/32.png) [@Thin\_Ice](https://boards.straightdope.com/u/Thin_Ice)\ **Post date:** [November 4, 2003, 12:35pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/9 "2003-11-04T12:35:56Z")
Seems wrong to designate 12 with an am or pm, but it’s understandable. There’s a 12 midnight and a 12 noon. 12:01am would be a minute after midnight and 12:01pm is a minute after noon. ---
**Author:** ![Zardoz](https://avatars.discourse-cdn.com/v4/letter/z/a8b319/32.png) [@Zardoz](https://boards.straightdope.com/u/Zardoz)\ **Post date:** [November 4, 2003, 12:55pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/10 "2003-11-04T12:55:23Z")
Does this mean Sweden uses 24-hour time exclusively? ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [November 4, 2003, 1:01pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/11 "2003-11-04T13:01:44Z")
> [@](#): > > \*Originally posted by Zardoz \* > \*\*Does this mean Sweden uses 24-hour time exclusively? \*\* In print, yep. You never see 5:00 meaning anything but 05.00 am. We often, but far from exclusively, speak in the 12-hour form, though. It’s discussed a bit more in the thread I linked to. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [November 4, 2003, 1:46pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/12 "2003-11-04T13:46:06Z")
Well, **Priceguy** , I guess I was a _bit_ off when thinking about the non-English-speaking world. But even in my personal experience, like I said, schedules and so on are always 24 hour formatted – no dispute. But in general people-speak, I’ve only really ever heard 12 hour format being used. In Germany, for example, dinner was at 5. The train left at 17:00 (spoken or written). Same thing in Mexico, but they’re a lot mixed. They use AM or PM as well as 24 hour clocks. Like on TV I sometimes see 24 hour format, but restaurants and such will use AM and PM. On that note, I’ll clarify that in Germany I don’t specifically remember “AM” or “PM” – I guess I didn’t realize that’s what you meant specifically, except for the midnight and midday references. My apologies. Hmmm… I’ve heard references to parts of Spain where they use a completely (to us) strange type of time system. I don’t even know where to begin googling. Anyone have any ideas? ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [November 4, 2003, 2:01pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/13 "2003-11-04T14:01:32Z")
> [@](#): > > \*Originally posted by Balthisar \* > **Well, Priceguy, I guess I was a _bit_ off when thinking about the non-English-speaking world. But even in my personal experience, like I said, schedules and so on are always 24 hour formatted – no dispute. But in general people-speak, I’ve only really ever heard 12 hour format being used. In Germany, for example, dinner was at 5. The train left at 17:00 (spoken or written). Same thing in Mexico, but they’re a lot mixed. They use AM or PM as well as 24 hour clocks. Like on TV I sometimes see 24 hour format, but restaurants and such will use AM and PM. On that note, I’ll clarify that in Germany I don’t specifically remember “AM” or “PM” – I guess I didn’t realize that’s what you meant specifically, except for the midnight and midday references. My apologies.** No need to apologize at all. And I do know that the 12-hour format is most common when spoken worldwide, but the specific “am” and “pm” designations are not. And this wasn’t meant to be any kind of debate anyway; I just needed a “translation” and got it. > [@](#): > > \*\*Hmmm… I’ve heard references to parts of Spain where they use a completely (to us) strange type of time system. I don’t even know where to begin googling. Anyone have any ideas? \*\* I took Spanish for a few years and never heard of this. That doesn’t mean it doesn’t exist, but it seems strange. ---
**Author:** ![Mops](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mops/32/16494_2.png) [@Mops](https://boards.straightdope.com/u/Mops)\ **Post date:** [November 4, 2003, 2:32pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/14 "2003-11-04T14:32:16Z")
The difficulty in understanding that the OP refers to does not seem to be 12-hour vs. 24-hour system but specifically the convention for 12 am to 12:59 am/12 pm to 12:59 pm. I also use the 12 hour system colloquially (‘let’s have breakfast at 9’) but I am stumped by 12.01 am because I’d expect 12:01 am to be two minutes after 11:59 am, like 11:01 am is two minutes after 10:59 am. To demonstrate that the 12 am/pm convention does not automatically follow from using the 12-hour clock: When using the 12-hour format Germans say **0 Uhr** for 12 am (midnight) **0 Uhr 30** for 12:30 am **1 Uhr morgens** for 1 am **12 Uhr** for 12 pm (noon) **12 Uhr 30** for 12:30 pm **1 Uhr nachmittags** for 1 pm Which convention, of course, also needs to be learned, like the 12 am/12 pm convention. ---
**Author:** ![Acsenray](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/acsenray/32/4519_2.png) [@Acsenray](https://boards.straightdope.com/u/Acsenray)\ **Post date:** [November 4, 2003, 2:38pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/15 "2003-11-04T14:38:25Z")
The day ends at midnight. The next day begins the moment _after_ midnight. Friday at midnight is the midnight between Friday and Saturday. 12 a.m. belongs to the previous day. 12:01 a.m. belongs to the next day. The Associated Press Stylebook: > [@](#): > > **midnight** Do not put a _12_ in front of it. It is part of the day that is ending, not the one that is beginning. ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [November 4, 2003, 2:46pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/16 "2003-11-04T14:46:58Z")
> [@](#): > > \*Originally posted by acsenray \* > **The day ends at midnight. The next day begins the moment _after_ midnight. Friday at midnight is the midnight between Friday and Saturday. 12 a.m. belongs to the previous day. 12:01 a.m. belongs to the next day.** Are you saying that someone saying 12am Saturday means the midnight between Saturday and Sunday? ---
**Author:** ![FatBaldGuy](https://avatars.discourse-cdn.com/v4/letter/f/ecd19e/32.png) [@FatBaldGuy](https://boards.straightdope.com/u/FatBaldGuy)\ **Post date:** [November 4, 2003, 2:59pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/17 "2003-11-04T14:59:06Z")
Now I’m getting confused!!! I’m thinking about my “instinctive” reactions to hearing these terms used. If someone says “midnight Friday,” I think of the midnight between Friday and Saturday. But if someone says “12 am Friday,” I think of the midnight between Thursday and Friday. In other words, midnight is the end of the day, but 12am is the beginning of the new day. I’ve never pulled this out and looked at it like this before, and I know it sounds illogical. Am I alone in thinking this way? ---
**Author:** ![Acsenray](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/acsenray/32/4519_2.png) [@Acsenray](https://boards.straightdope.com/u/Acsenray)\ **Post date:** [November 4, 2003, 3:51pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/18 "2003-11-04T15:51:45Z")
> [@](#): > > Are you saying that someone saying 12am Saturday means the midnight between Saturday and Sunday? Yes, that’s what I’m saying and that’s what the A.P. is saying. **Reepicheep** said: > [@](#): > > 12am Saturday means midnight between Friday and Saturday. **racinchikki** said: > [@](#): > > Saturday 12am means the midnight between Friday and Saturday I would disagree with both of these. Saturday at 12 a.m. or Saturday at 12 midnight or Saturday at midnight means the midnight between Saturday and Sunday, not the midnight between Friday and Saturday. ---
**Author:** ![Ebola\_Gay](https://avatars.discourse-cdn.com/v4/letter/e/a183cd/32.png) [@Ebola\_Gay](https://boards.straightdope.com/u/Ebola_Gay)\ **Post date:** [November 4, 2003, 3:54pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/19 "2003-11-04T15:54:36Z")
People, whether in America or elsewhere, who use 12 a.m. and 12 p.m. are not using their heads. (And that’s the nicest way I can put it outside of the BBQ Pit!) Because there is no such thing as 12 a.m. and 12 p.m., when these things are used, it can lead to unnecessary confusion (as evidenced by the OP). There is 12 noon and 12 midnight, and that’s that. Period. ---
**Author:** ![aerodave](https://avatars.discourse-cdn.com/v4/letter/a/f08c70/32.png) [@aerodave](https://boards.straightdope.com/u/aerodave)\ **Post date:** [November 4, 2003, 3:57pm UTC](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307/20 "2003-11-04T15:57:21Z")
> [@](#): > > \*Originally posted by acsenray \* > \*\*The day ends at midnight. The next day begins the moment _after_ midnight. Friday at midnight is the midnight between Friday and Saturday. 12 a.m. belongs to the previous day. 12:01 a.m. belongs to the next day. > > The Associated Press Stylebook: \*\* But 12:00:01 am (midnight and one second) obviously belongs to the following day. If all the seconds of 12:00 am belong to the day after, why would 12:00:00 itself (that exact second) belong to the day before? You can continue this problem down to smaller and smaller scales, like 12:00:00.00001. What you eventually end up with is a limit problem involving a discontinuity. The left-hand limit and the right-hand limit are not equal. The discontinuous function in this case is “day” as a function of “time,” and if the days are put sequentially up the vertical axis, then it becomes a step function. But I think that as far as the notation of time is concerned, the point of discontinuity is included in the right-hand side of the function. That is, based on the reasoning above, it ought to belong to the day after. Point is, if we called it **11:60** instead of **12:00** , then it would logically belong to the day before. But we don’t, so it doesn’t. [Next page](https://boards.straightdope.com/t/help-me-with-american-time-notation/211307.md?page=2)