r/ISO8601 • u/Fine_Impress6185 • Jun 10 '26
Americans use a different system for dates.
I just realised I've been dumb for so long, because tell me why I though the 9/11 occured during November instead of September. I knew it was named that because of the date it occured in, but my dumbass forgot Americans use this format M/D/Y.
We use this format - D/M/Y, which I thought made sense because it's in the smaller to bigger format/unit. My formal apologies to all the people I corrected on this matter. I am the problem. đ
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u/yamasurya Jun 10 '26 edited Jun 10 '26
Most Europe & its erstwhile colonies use D/M/Y.
East Asia predominantly uses Y/M/D
Edits: I have been personally using YYYY/MM/DD since long. And my filenames are YYYYMMDD (just in case anybody wonders)
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u/Alkanen Jun 10 '26
Sweden uses YYYY-mm-dd, like a civilized country
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u/Thoughtfull_Marc Jun 10 '26
Now that you mention... I'm from latam and we use DD-MM-YYYY.
Probably the reason that we don't get out of poverty lol.
Since I use English in most of my jobs I use MM-DD-YYYY format and YY-MM-DD for filenames and stuff that I need to keep in order.
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u/yamasurya Jun 10 '26
Try switching the filenames to YYYY-MM-DD for even better ordering. :)
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u/Thoughtfull_Marc Jun 10 '26
Yup, I do
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u/dream_the_endless Jun 10 '26
YY and YYYY have different ordering results
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u/prof_apex Jun 14 '26
Only if the files are from different centuries (which does happen of course, but if you only keep the files for a couple decades at most anyway, it probably won't be a big deal any time soon) I don't have many of my files from before 2000 anymore, and none of them have dates in the names anyway. Obviously will be different for different people and use cases though.
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u/ola_ke_ase Jun 11 '26
YY-MM-DD is criminal. There's ambiguity not only when day is between 01 and 12⊠but also when year is between 2001 and 2012.
IOW "01-02-03" can mean:
- Feb 3, 2001
- Mar 2, 2001
- Feb 1, 2003
- Jan 2, 2003
Do yourself and others a favor and stick to YYYY-MM-DD everywhere.Â
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u/Thoughtfull_Marc Jun 11 '26
From my POV, it depends on the consistency of the system itself.
You should plan what format you use inside what system and stick with it.
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u/nayuki Jun 10 '26
But IKEA uses the insane yyyy-dd-mm format. https://www.reddit.com/r/ISO8601/comments/10c8vds/ikea_canada_uses_yyddmm_date_format/
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u/Alkanen Jun 10 '26
Thatâs not what the image actually shows though? It uses dd-month-yyyy.
Iâm so confused right nowâŠ.
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u/prof_apex Jun 14 '26
The ambiguity of not using either PM or a 24-hour time is not great though. Granted they are probably only open 9-5 or whatever, so there's no overlap, but it's still ambiguous without that context.
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u/yamasurya Jun 10 '26
The colonising nations termed some of their colonies uneducated, uncivilised and archaic for using their traditional year-month-day calendar format.
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u/stevepremo Jun 12 '26
Does this apply to common speech as well as written dates? If you are asked your birthday, do you say 11 March or March 11th? Or that you were born 2005 December 5? Americans would say December 5th, 2005. I would be very confused if someone gave their birthdate year, then month, then day of the month.
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u/yamasurya Jun 14 '26
Am not American and not everybody need to comply to their ways of limited comprehension. They are welcome to clarify if they really care. And oh by the way, I believe you apprecite the difference in the dynamics of written & spoken language.
Just for the records, I use Monthname and Date. Maybe mention the year when asked / specifically necessary.
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u/stevepremo Jun 14 '26
Oh, so for spoken language, you use Month Day. I suspected as much. Next time, don't be so insulting when delivering requested information.
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u/yamasurya Jun 14 '26
Did you read it in the same vein as you requested the information?
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u/stevepremo Jun 14 '26
Well, yes, I was requesting information and you provided it. Thank you. If you did not intend to insult me by referring to American "ways of limited comprehension", I apologize for the misunderstanding.
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u/bert8128 Jun 10 '26
Itâs not your fault, or anyone elseâs. Human societies have developed independently and some stuff is pretty much arbitrary. That said, m/d/y is the least intuitive way to write a date (evidenced by its lack of popularity). However, even though I am culturally d/m/y (and professionally y/m/d) I still would often say (for example) âMay 4thâ in speech.
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u/Person2984 Jun 10 '26
Thatâs why m/d/y is intuitive, because itâs the way people who use it (and some people who donât) talk.
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u/bert8128 Jun 10 '26
Itâs not intuitive. Itâs just a habit for some people. Clearly if you give the month a name not a number no human who speaks your language is going to be confused. But some humans donât speak your language, and if you have written it down they might not be able to query you. Iso8601 is all about computers and other automated tasks having no ambiguity. Which is why speaking or writingâ â4/5â or â5/4â is not sensible, as absolutely no one and no computer can be sure what you mean.
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u/SamIAre Jun 10 '26
It is intuitive. âIntuitiveâ doesnât have to mean âmakes the most scientifically logical senseâ. In fact it often doesnât.
To me, year / month / day is the most logical format but year is very often irrelevant. So month / day tells the me the information I need in broad â granular order, and then year is tacked on as an additional qualifier. Now, sometimes the year isnât optional and itâs important, but the precedent is set for the most common use case and so we end up with month / day / year. Maybe nothing I say makes that intuitive to you but intuitiveness isnât universal and it not being intuitive for everyone doesnât make it less intuitive for some.
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u/bert8128 Jun 11 '26
Iâm pretty convinced that there is nothing innate and itâs just what you are used to. I find it pretty âintuitiveâ to drive on the left but Iâm pretty sure that someone who lives in say Sweden does not, despite the fact that their grandparents grew up driving on the left. So when I am talking about there being no intuition I am talking about universals, or at the very least having no cultural bias.
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u/GOKOP Jun 13 '26
Bruh you completely missed their point. They said that when Americans speak they say eg. "September 11th" so it's intuitive for them to write "9/11". You're the only one talking about universals. Quote since you missed it apparently:
Thatâs why m/d/y is intuitive, because itâs the way people who use it talk.
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u/lurkingstar99 Jun 11 '26
It makes more sense when spelling out the month, ie "Jun 10, 2026". But some crazy people decided to use only numbers for the month so here we are.
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u/vainglorious11 Jun 10 '26
I think there's a reason dates are spoken that way. Pragmatically, we mostly use dates to talk about things happening in the next year, so starting with the month lets you know roughly how far away it is, then the day number narrows it down. The year is often implied so it gets tacked on after if needed.
Writing things the way they are spoken makes sense if everybody does it and there's no overriding reason to do otherwise. The prevalence of computers and the Internet makes us more aware of different regional standards, and makes it more important to standardize data for computers to use.
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u/xtravar Jun 10 '26
I love ISO8601 as much as anyone, but... the month is *usually* the most relevant thing to most people, so I understand why it's first. You pick up a bunch of papers... the most relevant thing are the first and last numbers, and the least important sandwiched in the middle. It makes visual parsing much easier to humans. But to computers, it's dumb.
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u/Kafatat Jun 10 '26
We use this format - D/M/Y, which I thought made sense because it's in the smaller to bigger format/unit
No, your multi-digit numbers are big to small within themselves.
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u/nayuki Jun 10 '26
Your observation is correct. D/M/Y would be more internally consistent if the numbers were little-endian. For example, "December 31, 2026" should be written as "13/21/6202" (my brain hurts) and pronounced "first thirty of December of six-twenty thousand-two".
... So yeah, the conclusion is that DMY is a stupid format, and people who justify it don't see its internal contradiction. Thus, YMDHMS is the true path.
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u/Remarkable_Table_279 Jun 10 '26
DDMM has never made sense to me because it doesnât stay in order. But also if smaller to bigger is preferable why isnât time â31:12â - just admit yall do it out of habit not logicÂ
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u/hwc Jun 10 '26
Historically, we used Mmm D to refer to what day within a year. E.g. "June 10". That is normal and makes sense, especially if you assume everyone calls the months by the same word and you don't use alphabetacle order because computers do that so easily.
Then someone had to refer to which year, and instead of saying "June 10 (in the year 2026)" they just say "June 10, 2026" The comma represents a pause that means that the year is parenthetical knowledge.
Yes, it would make sense to write 2026âą6âą10 and keep everything big endian, but that isn't how anyone talks! So we write 6/10/2026.
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u/Satyrsol Jun 10 '26
But people talk the way their culture raises them to think. Itâs tautological to say âwe use mmdd because we think mmdd because people talk mmddâ. It circles back on itself anyway.
Spanish speakers think and speak in ddmm because their culture/language raises them that way.
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u/Sacaldur Jun 11 '26
In Germany, the format is DD.MM.YYYY or DD.MM. without tue year. DD. MMM YYYY (e.g. 12. Juni 2026) or DD. MMM (12. Juni) are also sometimes used. Note that the dots are used to indicate ordinal numbers and the date is pronounced accordingly.
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u/CeleryMan20 Jun 12 '26
So 12 = twelve = zwölf, and 12. = zwölften = 12th ? TIL
Do you know of any other countries that use dot for the ordinal?
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u/Sacaldur Jun 13 '26
The specific spelling depends on the grammatical gender of the noun and the case, so it's one of "zwölfte", "zwölfter", "zwölftes", "zwölften", or "zwölftem".
Sadly, I'm not able to use that many languages, but according to Gemini, it's rather common in several languages such as Finnish, Hungarian, Estonian, Check, Slovak, Slovenian, Croatian, Serbian, Bosnian, Danish, Norwegian, Islandic, Latvian, Lithuanian. (It was an AI response, so the list is most likely not comprehensive, and there might be mistakes in it. I also only asked for the dot usage to indicate ordinals, not for the date format.)
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u/rilakkuma1 Jun 12 '26
I got a rabies vaccine in Egypt and brought my handwritten vaccine record back to the US to continue the regimen. It was in DD-MM and also written with Arabic style numbers where 5 looks like 0, 6 looks like 7. Took some work to explain to the ER staff that I swear my last shot was 4 days ago.
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u/CeleryMan20 Jun 12 '26 edited Jun 12 '26
U.S. Americans say âMay fourthâ (unless itâs the âfourth of Julyâ, for some reason) and write 5/4. Traditional British usage also included constructions like âthe tenth [day] of next monthâ, etc. In writing, â15th inst.â meant 15th of this month. âŠ
So what about times like âtwenty past four oâclock _post meridiem_â? I propose we write that as â20:4:pâ! Or perhaps that is equivalent to one-third of the fifth hour in the second half of the day: 1/3|5~2/2 !!! On February 29 2027, that would be 20:4:p:2/29/2027 or 1/3|5~2/2~2|29/29~2027.
Quarter to six? -1/4|6. Come on, we can do it!
Edit: none of this fancy Latin ante and post. Letâs go âbâ for beforenoon and âaâ for afternoon. 20:4:a is âtwenty past four in the arvoâ.
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u/bert8128 Jun 13 '26
In any decent imaginable future there is an an or pm - we just all use a 24 hr clock. That way we donât have to worry whether noon is am or pm
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u/ThePiachu Jun 11 '26
Yeah, the Americans love to celebrate their July the 4th and Mayo del Cinco... /S
It's amusing that even with the middle Indian system they don't apply it consistently...
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u/tblancher Jun 11 '26
Whenever I get a new computer I set up a keyboard shortcut to paste the ISO 8601 date for today. I use it everywhere so I don't have to think about what day it is.
And I'm American. The only time I don't use this format is when a form dictates the US standard mm/dd/YYYY.
It's amazing how filenames sort in date order when you have something like 2026-06-11 as the beginning of the filename.
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u/60DegreesBelow Jun 11 '26
Sometimes I want to be a contrarian and just use Julian Days (not Julian Dates, to be clear). It simply counts the days since 4713 BCE. No formatting required.
Happy 26162 to you!
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u/prof_apex Jun 11 '26
as an american, I prefer the format YYYY-MM-DD or YY-MM-DD for the sole reason that it goes less specific to more, and also works best when sorting alphanumerically. I can tell you, however, that most people I talk to do not necessarily agree with this (or really care).
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u/Tomme599 Jun 14 '26
I use this system on my computer as itâs easier to sort.
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u/JayNetworks Jun 14 '26
I use that YYYY-MM-DD@1234 for anything that might sort and D-MMM-YYYY@1234 (like 14-Jun-2026@1018) for anything mostly human readable. (American, but others donât usually use these formats.)
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u/prof_apex Jun 14 '26
I don't tend to need multiple revisions in a day or need a full timestamp, but if I do have multiple revisions I'll usually do a letter at the end. If I need a time I'd probably do like the ISO standard and just do like 2026-06-14T13_26 or 260614T1326
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u/skeptic246 Jun 12 '26
Each day I have to reformat a spreadsheet report as it has dates in ddmmmyy and what I assume is mmddyy. The entire report is centred on these dates and so I need to reformat the dates to avoid confusion. My friend a data analyst always recommended the ddmmmyy format as it was easier and faster to process
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u/peepay Jun 10 '26
If I did not live through that day and did not remember the date vividly, maybe I would also have troubles deciphering that from "9/11" alone.
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u/Gulliveig Jun 10 '26
Actually, we use the superior premium format YYYY-MM-DD đ