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Why is the most common date format in the US like mm/dd/yyyy, whereas in Europe (including the UK) it's more common to have dd/mm/yyyy?

Looking around, I found that the US form is actually the more traditional Anglo-Saxon way, but the British adapted to using the European form in the early 20th Century.

But I couldn't find a definitive discussion of the history of the different formats. Is it just conventional, or is there an official 'British date standard' (like with metric and imperial, for example).

Dan Blows
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    There are no "rules" -- but there is rigidly enforced convention in order that everyone knows what everyone else is talking about. Not quite sure whether this counts as ELU or not, though. – Andrew Leach May 24 '12 at 12:00
  • Vaguely related: How to write out dates correctly – Matt E. Эллен May 24 '12 at 12:27
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    Anglo-Saxon (i.e. English ca. 500-1100 AD) dates were written in full sentences (e.g. "fifteenth day before the calends of April" -- Anglo-Saxon Chronicle) rather than using any kind of notation. At least, that's been my experience. Is that what you really meant to say? –  May 24 '12 at 16:20
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    I think it depends on the context. In the UK, for example, for "information interchange" something similar to ISO8601 is ratified as BS ISO 8601:2004, BS EN 28601 standards (which are preferred). So the format yyyy-mm-dd became pretty common on official documents, manufacturing stuff or interfaces. – oxygen Apr 11 '13 at 00:23
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    I have no sources to quote as such, but personally prefer to use a logical format starting with the lowest unit (days) and ending with the highest (years), thus the 4th of July would be most logical (to me anyway) in European format as 04/07/13, not 07/04/13. –  Apr 19 '13 at 23:36
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    @user42857 actually the Japanese version is the most logical, considering that time is written in opposite order starting with the highest number and ending with the smallest. They have adapted this to the date as well, so its yyyy.mm.dd hh:mm:ss (not sure about the delimiter symbol). – Otto Abnormalverbraucher Mar 15 '18 at 09:25
  • @OttoAbnormalverbraucher that isn't Japanese format, that is the international standard (ISO 8601) date format which is used by many countries. – Tom Nov 20 '19 at 15:13
  • @Tom The ISO 8601 was only published in 1988 but it existed long before. And yes, I'm aware many other countries use it. I didn't know the ISO number so I just called it the "Japanese" system (afaik Japan was one of the first countries to fully adopt it) as I would call MM/DD/YYYY the "American" system ... you figured what I was talking about. – Otto Abnormalverbraucher Feb 28 '20 at 20:35

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Although there are people who will sometimes say:

  1. Today is Thursday, the 24th of May, 2012.

There are also others who instead say the same thing this way:

  1. Today is Thursday, May 24th, 2012.

Certainly in the United States, the second way of mentioning a date is more common than the first. The long form sounds more formal to us, as in “on the Fourth of July” being more formal and long-winded than simply saying “on July 4th”.

It was pronouncing the month before the day out loud that gave to retaining that same original order when converted to digits: merely convert the month name to a natural number, and there you have your answer. What’s today’s date? It’s May 24th. Instead of writing May-24, we simply change the “May” to “5” and write 5-24 or ⁵⁄₂₄.

That way it follows the natural language order and so requires no mental gymnastics to switch things around when speaking the date aloud. Similarly “September 11th” gets written ⁹⁄₁₁, etc.

The full spoken form with the year, “May 24th, 2012”, then becomes the written shorthand “5/24/2012”, or often just “5/24/12”. “Christmas of 2001” can be, and somewhat annoying often is, written “12/25/1”, while “January 25th, 2012” becomes “1/25/12”.

This isn’t usually any sort of problem because of universal consensus on how to interpret such things in the United States. If you write day/month/year in America, you will not be understood. Although I myself prefer the ISO notation, normal people do not use it in their daily affairs.

tchrist
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    I don't speak it that way. I say "Thursday the 24th of May" but then I'm British. – Andrew Leach May 24 '12 at 12:53
  • @AndrewLeach ˋdateˋ == Thu May 24 06:55:20 MDT 2012. – tchrist May 24 '12 at 12:55
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    Fortunately we all have our own culture-specific Date::Format routines :-) – Andrew Leach May 24 '12 at 13:02
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    I had a look at some 17th century books that use all sorts of formats, for example: 15 of October, 1647 / Thursday the 10th day of October / October, 24. 1671 / October the 11th 1695 / 1687 October 21. – Hugo May 24 '12 at 13:13
  • @choster No of course not. I’m saying that we would never write nor say “the 4 July”. Note the difference. We simply do not read “25 December” aloud as “the 25ᵗʰ of December”. If we expect/want the expansion, then we write it out. “The Fourth of July” is a perfectly normal construct, but never would “4 July” be taken to mean that, because we do not convert cardinals in writing into ordinals in speech. We use ordinals in writing. We don’t pretend cardinals in writing are actually ordinals. – tchrist May 24 '12 at 15:10
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    Most countries that use 24hr clock still talk in 12hour clocks in normal speech. So you would write 17:30 but say half past five in French - or confusingly half to six in German – mgb May 24 '12 at 15:40
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    I don't think there's a very strict correlation between how dates are written and pronounced. I might see any number of these over the course of a month: May 24, 2012; May 24th; 24 May; 05/24/12; 24/5/2012; or even 20120524, and I might verbalize them in any number of ways: May twenty-fourth; the twenty-fourth of May; twenty-four May; or even "five twenty-four", depending on the context. The way I say a date doesn't necessarily match the way it's written. If asked a librarian for Tuesday's newspaper, I might be apt to say, "Can I get the paper from 22 May," even if the banner reads "May 22nd." – J.R. May 24 '12 at 15:45
  • @J.R. Are you disagreeing that Americans write ⁵⁄₂₄ for May 24 because it corresponds to the order that they typically say the date aloud? As far as I know, that’s the standard and accepted explanation. – tchrist May 24 '12 at 16:09
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    To be clear, no, I am not disagreeing with that assertion. Here's what I am saying: even if that was biggest factor in choosing the 5/24 standard over the 24/5 format, that doesn't mean everyone always says a date the same way - there's too much variation to make that claim. – J.R. May 24 '12 at 16:32
  • Since you've added more stuff, I've got a couple more comments: (1) U.S. military date formats (e.g. 24 May 12) are nicely unambiguous, and worthy of a mention; (2) I like to (jokingly) point out ISO 8601 is a ticking time bomb: it's a long way off, but our ancestors will eventually need to deal with the Y10K problem. :^) – J.R. May 24 '12 at 16:36
  • @J.R. Actually ISO 8601 allows for a 5th year digit if agreed upon by both parties. It’s Y100K where the problem hits. – tchrist May 24 '12 at 16:59
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    Re your edit, I didn't downvote (or upvote) but the problems may include the following. You say US order follows the 'natural language order' but I don't think that makes sense as those of us in other countries find the DMY order natural. You say that the US format is because people (in the US?) talk like that, but how do you know it's not that people in the US talk like that because that's the official date format? If the latter then you haven't answered the question. You say there are plenty of references on the web, perhaps you could provide links to the more persuasive ones? – Gaston Ümlaut May 25 '12 at 01:36
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    The question is actually two explicit questions and one implicit: why do the US and the UK differ? What's the history? And is there an official British standard? This doesn't answer any of those questions: it answers the related but very distinct question as to why the US convention is what it is. – Peter Taylor May 25 '12 at 11:33
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    Because of the ambiguity that arises for the first 12 days of every month, I prefer either yyyy/mm/dd or dd/mm/yyyy so that one is either getting more or less specific as one goes along, not jumping from month to day to year. Being in the computer industry, I really prefer yyyy/mm/dd because it alphabetizes better. – TecBrat Jun 04 '12 at 04:02
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    It makes no sense to justify the order of MM/DD/YYYY based on how the date would be spoken aloud in day-to-day conversation. If you're using numbers to represent a date, there should at least be some numeric logic (as opposed to aesthetic/heuristic logic) justifying the order of numbers. Personally I'd love nothing better than to see middle-endian date notation abolished and the US stick to a more sensible formula... if people find it more logical to put the month first, they can stick to writing "Oct 3 2013" or something similar instead... –  Jun 05 '13 at 10:55
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    @J.R. Concerning Y10K or Y100K: I think are ancestors have no problem there; our descendants, on the other hand might. – Andreas Blass Jun 17 '13 at 02:20
  • @TecBrat Another way to describe the advantage of the yyyy/mm/dd format is that, not only are the three parts (y,m,d) in a one-way order, but all eight digits are in a one-way order. By the way, I believe the yyyy/mm/dd format is standard in Hungarian. – Andreas Blass Jun 17 '13 at 02:22
  • @AndreasBlass: You're right about that – I can't believe I messed that joke up! – J.R. Jun 17 '13 at 02:35
  • tchrist, I believe you are correct. I grew up in America and never thought about it. Having become familiar with the European way, however, I now find our way illogical. It makes much more sense to me to write it in the ascending or descending units format. Also, I now use the yyyy/mm/dd format to name computer files so that they are listed chronologically. – sarah Jul 06 '13 at 08:34
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    @tchrist In the UK, we would say the 24th of May, 2012 or Thursday the 24th of May 2012 (with or without a comma/gap between the moth and year), even for a date written as 2012-05-24. Therefore, the natural writing order to use is 24/05/2012 – a lot of Britons find 05/24/2012 quite jarring, since it takes at least 5 seconds to realise that it's written in the American format. – Toothbrush May 07 '15 at 19:01
  • @tchrist I believe the explanation as to why this kind of answer would receive so much hate or down votes is due to your phrasing of "we speak" and "the natural language order", which implies that this is the standard everybody should follow instead of indicating you're referring only to Americans. – Myzifer Dec 13 '16 at 16:33
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It's very possible that the US inherited this from an outdated English format - much like the length unit, after Henry III's foot and which the English have left behind in favour of the more logical metric system.

One argument I've heard in favour of the American system of dating is that the numbers of months in a year is smaller than the number of days in a month which itself is smaller than the number of possible years. So you would have 12/31/2013, in ascending order. I don't really buy this argument, but OP might be interested in it anyway so here it is.

Meanwhile, in Northern Europe they've moved on to an opposite, descending date standard: year/month/day.

Corina
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    That’s simply ISO 8601 format that uses YYYY-MM-DD. The rest of your diatribe against the traditional English measurement system is simply misplaced bigotry and has no place here. – tchrist Jul 05 '13 at 18:27
  • I argue that it's very relevant, if the US preserved various systems used in England before it achieved its independence. But ok? – Corina Jul 05 '13 at 18:32
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    @tchrist: It didn't read as a diatribe or as bigoted to me. It was one sentence, with one concrete example (the foot), given to corroborate the plausibility of borrowing from the English. The closest thing to a "value judgment" in the whole thing is that the metric system is more logical than the old English (and current American) system. But the thing to that is, I don't even see Americans ever argue that feet/inches/miles/etc. are more logical than the metric system. Honestly, that judgment isn't in serious dispute, anywhere. – John Y Jul 05 '13 at 18:54
  • Many English people still regularly use feet/inches, especially when referring to things such as height. All road signs are exclusively in miles, as well. Metric tends to be commonly recognised, but most prevalently used in scientific & technical contexts. – Myles Feb 07 '18 at 16:13
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The 29th of May Is Oak-Apple Day. Ring-a-ding-ding! Long live the King!

That was an old rhyme celebrating the return of Charles II to Britain at the beginning of the Restoration in 1660.

I like to abbreviate dates as day/month in Roman numerals/year, with periods/full stops rather than "/" between the numbers, such that today is 31.vii.2018. Sometimes I make the last "i" a "j" (an affectation, I know, and a throwback to ancient manuscripts), and drop the "20" in the year, so that I have "31.vij.18". A month-number in Roman numerals can't be mistaken for a day-number. My way is not perfect: I don't think O-W Kenobi would write "4.v. be with you", for example, but then, he wouldn't write "5/4" or "4/5" either. He would write out "May the 4th...".

(I spent several years in the military when I was much younger, and got used to the dd/mm/yy format used in the US military. I surmise that the US armed forces adopted this format during World War I, to minimize confusion with allies, but I don't know for sure.)

tautophile
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Personally if I was to say a date I would do so in the format mentioned by Andrew Leach, or even 'the 24th of May'. I suppose it depends on what you're used to. The American date format often has me confused unless the month is spelled out.

Alex
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  • I think you should only use were in this context if it is contrary to the fact. For example 'if I were you' as opposed to 'if I was you'. – Alex May 24 '12 at 19:55
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    I agree with you that using were is correct if the subjunctive is contrary to the fact, as furnished by the example 'if I were you', however the sentence '..if I was to say a date I would do so in the format...' does not contain anything to the contrary, hence was is acceptable. – Alex May 24 '12 at 20:45
  • To re-iterate, 'were' should only be used if the subjunctive is contrary to the fact. So I used 'was' in this instance, which I feel is acceptable, you obviously don't. Well I aim to continue using 'was' where I feel it is appropriate. – Alex May 24 '12 at 21:00
  • Wales and Welsh (but not fluently). That's how I distinguish between were and was. Perhaps we should agree to disagree as I am being warned to avoid extended discussions. – Alex May 24 '12 at 21:16
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    @tchrist This is not relevant to the question and should be taken to chat. Anyway, what's your data to show that native English speakers don't use 'was' in that way? – Gaston Ümlaut May 25 '12 at 01:40