Ask HN: What does 12:00 AM mean?
Today I missed my online exam because I was 12hours late. Being European and engineer I was used to 24hours notation. “12:00 AM” was interpreted as 12:00 noon in my head. In retrospect i’m disappointed Pearsonvue (in this case) does not write these times in universal format or even better, attach an ics file upon schedule confirmation.
My question to you is: did you run into this kind of mistakes also? How do we solve this more universally?
220 comments
[ 5.0 ms ] story [ 242 ms ] threadIt would have been 00:00 for you.
It's possible to mix up dates and times from each other too (is 12.30 Dec 30 or half past noon?)
Why GP would have exams at midnight is anyone’s guess, but the example can only be interpreted as just before midnight.
11:59pm would be 23.59 in other places. The mere use of "11" would suggest morning.
11:59pm is 23:59 (in 24h)
afaik everywhere...
but if i understand it correctly:
12:00pm is 12:00 (in 24h)
12:59pm is 12:59 (in 24h)
01:00pm is 13:00 (in 24h)
No, it does not. We 24ers read clock. 11 doesn't suggest morning.
March 24 at 11:59pm
That would be close to:
March 25 at 12:00am
A bit less confusing but still:
March 25 at 00:00am
https://kimiwo.aishitei.ru/i/ytPbouZ21iYnNXi7.png
Not all too uncommon to see bars and bookstores open until 27:00 or 28:00 and it's surprisingly intuitive when you consider when the bar is open. ie 19:00 ~ 29:00. (7pm - 5am)
12:00 AM is one minute before that.
Midday and midnight are the points at which AM/PM change and you can't logically differentiate them by appending AM or PM. You just have to know the arbitrary cultural convention that midday is PM.
12:00 and 12:01 are both in the 12:XX hour, but 11:59 and 12:00 are not. Of course the whole thing is arbitrary, but the convention is that the 12:00 - 12:59 hour is PM, rather than just 12:00.
Which is strange, because it does not follow the concept that all other of those time"stamps" do.
12 AM implies that 12 hours of something has passed, but it's nothing that we would align our lives against. And why is 11 AM after 12 AM on the same day? There's no logic (ok, some, but... well... a strange one) behind that.
Ante- meaning “before”, meridium meaning “highest point of the sun” as in when the sun crosses the “meridian” which would be the line in which it is now setting instead of rising.
Passing from post-meridian to ante-meridian is exactly 12 hours from when the sun passed the meridian point, to keep it “consistent”.
I get though that it’s confusing, I questioned it a lot as a young boy.
Personally I believe that is stupid that we go from 11pm to 12am, but the reason is that the cutover is “12”, and everything after 12 (including the hour) are considered morning.
Like others have mentioned, we should really be using 24hr time these days where possible. Additionally I’m of the impression that we should use ISO8601 for date formats instead of what the Uk does (or even worse: what the US does).
It's like using metric. Just use it.
"dies" is the Latin word for day. It is in the e-declension. Not many words in Latin have the e-declension. Another one is "res", the Latin word for thing.
I don't know a lot about "meri", but it seems that "meridies" is also in the e-declension.
"ante" and "post" are prepositions which ask for the accusative. The accusative is mostly lost in English, but often when you say "me", it's accusative. If you say "after I" it feels wrong. You say "after me". German has preserved the accusative, so it is natural for me.
Now, in the e-declension the ending for the accusative is "-em". So you say ante meridiem and post meridiem.
For example, I could say that you're ignorant of the harm that the colloquial use of "retarded" has on disabled people. I could say that you're being needlessly obtuse or selfish by claiming that you should be able to call things "retarded" despite polite requests to stop. I could say that you're callously dismissive of disabled people who are asking for you to stop using the word "retarded" as an insult.
> When disagreeing, please reply to the argument instead of calling names.
If you were to use it properly, you'd say "societal progress has been retarded by the U.S." you wouldn't say "the U.S. has done something retarded"
Time is a hard programming and engineering problem. Adopting a global UTC on a 24 hour clock would resolve most of this, but people are entrenched.
Solves so many problems.
Now, Django supports this pretty cleanly so it's often pretty easy to enforce and work with.
In the "correct" usage, you have an illogical jump between 11:59 AM and 12:00 PM.
E.g. despite abortion clinics having a history of being violently attacked and often "regulated" out of existence, only roughly 20% of Americans think abortion should be flatly illegal outright and the labels "pro-life" and "pro-choice" seem to be self-applied in roughly equal proportions:
https://news.gallup.com/poll/1576/abortion.aspx
Granted, abortion is a complex and sensitive topic even before you bring religious doctrines into it, but it only takes one snowflake with a gun to think changing the clocks is Satanism for someone to get hurt. I'm frankly amazed the DST change seems to have passed so easily given the kind of conspiracy theories that would lend itself to.
/s
just because you got used to meaning of this nonsense, it doesn't mean it's right
But to your question, yes 12:00 AM is midnight. It's the 12 o'clock that's at/after midnight, while 12:00 PM is the 12 o'clock that at/after noon.
so how many quarter inches are the footegg fields these days?
/s
I always write my Chinese colleagues time either in Chinese/Beijing time or Berlin time to clarify what time zone we are talking about, because it's not so obvious since some of them work until midnight or even 1AM local Chinese time
The Ante Meridian / Post Meridian explanation works better. Still, it is a fucked way to say time.
By the way 24h analog clocks exist too.
Anyway that is not really the problem, we just learn from being kids that 12 is only valid for noon otherwise it is implicitely 0 as the next one is 1 anyway. And, at least in my country, we rarely say 12 as we use our words to say midnight/noon.
I'm American so I don't really know, do Europeans generally ignore how AM/PM works?
IIRC the Romans created the system, so I'd find it really weird if it had dissapeared from common usage around there.
Also, every single picture I've found of a clock tower from Europe seems to follow a 12-hour convention.
Not in Britain we don't. Analog clocks were abolished by Henry VIII. Since then we kept time using sundials until digital watches were invented in the 1970's and Roger Moore wore one playing James Bond in 'The Spy Who Loved Me'.
12:00 PM is noon because one minute later, the sun is past being directly above. That is, it's 12:01 Post Meridiem. Since it would obviously be nonsensical for 12:00 AM to be immediately followed by 12:01 PM, noon is 12:00 PM by convention.
Extending this logic to midnight is left as an exercise to the reader.
Don't feel bad, I don't think anybody explained this to me until I was almost 30.
You jump from "sun is overhead in 12 hours" (12 AM) to "sun is overhead in 1 hour" (1 AM) when you follow that logic.
The 12 hour-system is broken and should go away.
Besides, at this point 90% of the time formats people look at in their daily lives are probably digital (since analog faces are only relevant to actual clocks and even most clocks are likely digital simply because so many electronic devices come with digital clocks) and even analog clocks don't always have numbers on them (or use fanciful alternatives like Roman numerals). The people who prefer analog clocks are clearly just sticking with them out of personal preference or aesthetics anyway.
How is that different than 11 -> 12 > 1 ?
Yes I get it that in normal integers, 1 is not after 12, but neither is 0 after 23.
The 24 hour system: 23 -> 0 -> 1
The 12 hour system: 11 PM -> 12 AM -> 1 AM
In the 24 hour system, there's a single point where the new day starts, and it's the transition from 23 to 0.
In the 12 hour system, where does the new day start? Numbers tell you it's 12 -> 1, but it's actually 11 -> 12. You have no way to figure the answer to OP's question out without additional context.
As others already pointed out in this thread, a 12 hour system using 0 instead of 12 would make it much more intuitive, although now you'd end up with either using 0:00 PM for noon, which feels strange, or using 0:00 AM and 12:00 PM, which is inconsistent. The 24 hour system has no such issues and has a massive advantage over creating new systems - people are already familiar with it.
I honestly am trying to understand the point being made. Isn't when the day starts obvious in either case? We know when the new _day_ starts because the date rolls over at that time. No one thinks the day starts at 12:00 in the 24-hour system, or 12:00pm / noon in the 12-hour system?
> ... there's a single point where the new day starts ...
Is this what you're saying: that in the 24 hour system, there's one point in time where the clock resets from a high number to zero, and that's also when the day starts. Therefore, it is "not confusing."
I felt rather that the problem the OP stated was simply "I am used to the 24 hour system and I was communicating with someone who was used to the 12 hour system. They naturally gave me a time of 12:00am but I didn't notice that am part and assumed they meant the same "12" that I understand as "12" in my system. So I missed an exam."
That's an additional reasoning you have to do in order to explain the non-intuitive fact that the new day starts when transitioning between hour 11 and 12. You can't come up with that conclusion based on clock system alone, you need to reach for the calendar. It makes you jump additional mental hoops, making it error prone (as evidenced by this thread).
> but I didn't notice that am part and assumed they meant the same "12" that I understand as "12" in my system
No, people who use 24 hour system are usually familiar with 12 hour system as well (guess what's there on analog clocks?). It's just this one special case of 12 AM/PM that's confusing, because you can make convincing arguments for having it both ways.
But since the midnight is the same distance from the noon, before (AM) or after (PM), in theory both should be reserved for midnights (the past one and the future one), and noon, too, should be both AM and PM - at 0 hours.
The only real solution for this mess is the one that everyone uses: just burn the meaning of 12:00 AM as midnight into your brain, and those who fail to do so are in for a trouble.
I do understand that having two different 12's in a day introduces an ambiguity about which one is the "real start" of the day just based on "12:00" alone.
[0]- Lore is that the sundial and dividing the day into 12 sections happened before the invention of the number zero, but I don't know if this is accurate.
Use this as an opportunity to realize that moving forward you need to be sure about times — especial for things that really matter. Using your European-ness and the fact that you’re an engineer isn’t an excuse. You can be disappointed in software and other people for the rest of your life and keep missing important appointments if that’s what you want.
Europe and America do not only time differently, but phone numbers (1-800-123-1234 in the USA, 06 86 57 90 14 in France), dates (Jan 1 1911 would be 1/1/11 in the USA, 11-1-1 elsewhere), decimals (1,000.00 or 1.000,00), units (inches vs centimeters), reading order, daylight savings time, time zones (some countries don't even have them), etc. To say nothing of language and cultural differences, just formatting basic facts.
You don't solve it "universally", you make affordances for diversity the same way you allow for light/dark mode or language or any other user preference.
Not even all calendars have proper embedded time zone information so that's not always reliable either.
There is Unix time but you still have to convert that according to arbitrary rules, especially for countries that observe variable daylight savings like the US.
It gets even harder when you have to do math, like 00:00 Jan 1 1970 plus 30 years isn't automatically midnight of Jan 1 2000. It depends on whether you mean 30 * 365 24-hour days or some # of quartz vibrations or 30 * orbits around the sun or 30 * years of a certain country's time (adjusted for leap years and leap seconds and daylight savings and time zone changes mandated by new laws). There is no "right" answer. Libraries like Luxon or Momoent can help, but it's never easy.
That's just the reality of a multicultural business world. When in doubt, double check and reconfirm.
This is a ludicrous and typically American-centric assertion. It is Americans who steadfastly refuse to use international norms, whilst asserting that their antiquated systems are "better".
The vast majority of the world writes dates either YYYY-MM-DD, or DD-MM-YYYY. Only America uses the (nonsensical) MM-DD-YYY system.
The vast majority of the world uses the metric system for all measurements. Britain only partially uses the Imperial system. Only America (and partially Canada) use the US customary system (which is different from the Imperial system.
The vast majority of the world measures temperatures in Celcius. Again, only America (and to a small extent Canada and old people in Britain) chooses to use Fahrenheit.
But the US isn't the only place with different practices.
China has no time zones. New Zealand's Chatham Island has a 45 min time zone, as in UTC+12:45. Some institutions use lunar or cultural calendars instead of Gregorian time. Some don't use Arabic numerals outside of Western collaboration.
Time aside, the US, Canada, Chile, Colombia, the Philippines, and a few other places use letter-sized instead of A4 paper. Phone number formats are different everywhere. The time and decimal separators are different in many places. Time and timeliness (as in how important it is to start and end on time) differs by culture. Preference for information density vs simplifying cognitive load (in the UX sense) differs between languages and cultures. Red is a warning in some cultures and good luck in others. Not all colors are even distinguishable between cultures. Do you act casual, or formal? Keep your distance or offer a touch? Right hand, left hand? Is pointing OK? How long should you maintain eye contact? First names, last names? Many cultural systems don't identify people like that. Nodding isn't a universal gesture. Do you do a haka before events? What about a ritual blessing before a competition? There are SO many differences to consider in an international context.
Big companies have entire departments working on this stuff, not because they are ludicrously US-centric, but because it's so different everywhere.
I only mentioned the US vs Europe differences because that's what the OP asked for. Shrug. I'm not shilling for the American ways, just describing them. I wish we went metric decades ago, because it's a far superior system.
But the thing about standards: everyone has their own.
Except for times and angles (only the second and the radian are SI). Also, aviators everywhere outside of PRC and North Korea use feet and flight levels (hundreds of feet) for altitude, and navigators (in the air and at sea) use nautical miles and knots. Other widely used non-metric units include mmHg for pressure, AU and parsec for astronomical distances, and eV for energy.
Many Americans would use standard _given the opportunity_. Nothing here was ever converted, or has the same availability in metric so things continue on as they always have. Very few defend them as better, especially distance measurements.
Claiming there is a "better" system for dates is just preference. Why does it make sense to list the year first, it only changes once every 365 days?
It makes more sense as MMDD-YYYY or (MM-DD)-YYYY. The Month-Day is a single thing, there are 365 of them in a year, in a roughly base 30 counting system. The year can often be left off when colloquially referring to a date (3/14 or 0314 for example.)
I think it makes more sense to have DD/MM as the day is the thing that changes more often and thus DDMM starts with the most important information first.
Also if I think I never encountered someone looking at their digital watch to know what Month is. But always people check phones/watches to know what day is. So why would these systems start with the less important information for the user?
Day before month creates some ambiguity regarding if you’re talking about the near past or near future.
If you consider MMDD a single unit, it doesn’t make sense to represent it backwards. You need to be able to tell that 0402 is a bigger base iterarion than 0302. If it’s DDMM 0203 and 0204 don’t appear to be an entire base count apart.
I am talking about what makes sense for people. And most of the people look at the calendar to know what day is today.
Regarding time, if you are asking me I will put minutes before hours in our era where every minute counts.
But before this speedy times, people where mostly concerned with hours.
We got European/UK roots but since US is next door, in real Canadian fashion we just simple do both. Arbitrarily.
- driving distance and speed is measured in KM and KM/h
- but height, home construction and day to day distance we use imperial. So I'm 5'9" not 175cm. and McDonald's is 100 feet from the intercection, but the next offramp (speedway) is in 3km
- food is all in imperial, so grocery is in pounds, we buy a 12.7oz pint. But liquor stores/bottles are in ML. but if your talk to friends about what to bring to a party, it's back to pint or a "Mickey" or "26er"
- science is all taught in metric.
- But unless you talk cars and motor output, it's back to horsepower (this one is actually pretty common still everywhere in the world).
- And we use centigrade instead of farenheit. So small talk with Americans at work is a constant math excercise.
- Dates are complete utter toss up in the air. My driver license is YYYY/MM/DD, but i know for a fact I've filled out forms that goes MM/DD/YYYY (at the doctors office), and i'm just conditioned to go MM/DD/YYYY when typing dates online because that's how I say it. I don't say 25th of March, I say March 25, 2022.
The US armed forces use metric, right?
You also need to recognize ambiguity and ask for confirmation when you see it. Even in the US people will get confused by 12AM/12PM; when you see either of those times you should double check to see what the person meant. On the other hand, the person setting the time should also have recognized the possible confusion and clarified (i.e. 12 noon or 12 midnight).
There is a reason insurance policies in the US tend to start at 12:01 am.
Lots of folks here are trying to logically determine which use is “correct”, but it doesn’t really matter much if the reader doesn’t agree and misinterprets. So the best option is to use an unambiguous alternative like above.
For more, see https://en.wikipedia.org/wiki/12-hour_clock#Confusion_at_noo...
I understand that it comes from analog clocks, but when represented on anything else it feels wrong.
14:01 -> fourteen oh one
14:10 -> fourteen ten
etc
Fourteen o'clock works too but is less natural.
WTF is 'military time'?
That's an ordinary 24 hour clock. Rather bizarre to call it "Military" time.
Military 1400 - fourteen hundred 1430 - fourteen hundred thirty
Standard 24h 14:00 - fourteen hours 14:30 - fourteen thirty
But I am not native English speaker and this is only my understanding from what I observed about military time vs 24 hours time and I may be wrong, someone please correct me.
I missed a perfect score in my first geography exam there, where we had to calculate timezone, exactly because of this... I thought it was so much more logical to have 12am follow 11am... I was very annoyed to not get 100 in that exam just for such an annoying format...
In retrospective it does make sense actually... as soon as you pass noon (meridium) you are in the post-meridian, not ante anymore...
Better would be if the formst would use 00:00am and 00:00pm... This way you would have a switch from am to pm and v.v. when the time goes from 11:59 to 0, i stead of to 12.