Almost everywhere outside the United States, when short dates, e.g. 01/02/2013, are shown on computer screens, the user can't be sure whether the first two digits represent the day or the month. Is it January second or February first?

This is a big problem for people outside the United States, as they encounter both formats regularly, and can't know if the system has adapted to their locale, or has stuck with the American format. But I assume American users see mostly the American format (because many, if not most, information systems are built by or for Americans). What I'm curious about is whether American users also are confused in this scenario?

If you can point to some evidence or research, great. If not, I'll settle for your knowledgeable experience.

Note: I'm not asking for the wonderful solution of naming the month, e.g. May 21, 2013. I'm asking about the cases where a short date format has to be used.

  • 4
    I always fail when going into a ps3 game site that asks age confirmation and there's input fields defaulted like "01/01/2013", even if the inputs are dropdowns, I first try typing 14 into the first, and then I notice that the dropdown has max value of 12, so then I type the 14 into the second field and put the month in the first one. I'm from Finland and we have dd.mm.yyyy.
    – Samuel M
    Commented May 21, 2013 at 6:33
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    SamuelM and JohnGB, we are Europeans, and we encounter both formats. Of course we are getting confused. But in the States, people might always assume the format is the American one. I want to know if they also confuse the day and the month.
    – Dvir Adler
    Commented May 21, 2013 at 6:42
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    I am an American and I get confused, never realized the date formats were American VS the rest of world. I always just assumed some people liked the month first and others the day first.
    – stoj
    Commented May 21, 2013 at 15:59
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    No, I'd say almost everywhere outside USA people would be sure that the 01/02/2013 is 1st February, since middle indian format would seem so absurd to them that they wouldn't even think someone may use it. I have noticed that on some forums the posts are not sorted correctly by dates, and some posts are in future, but I haven't even thought that month could be written first! Imagine the time 44:12:21 and guess what time it is :D:D
    – user5558
    Commented May 21, 2013 at 19:27
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    Relavant XKCD
    – Doresoom
    Commented May 21, 2013 at 20:33

7 Answers 7


I don't have a pointer to published research - but in my experience US folk will always assume the US MM/DD/YYYY format unless they are knowingly using an non-US site, and are already aware of the potential differences.

If you have to use numbers only then the format that causes least confusion across cultures in my experience is YYYY-MM-DD since it differs from both "defaults" and doesn't suffer from any assumptions.

That said using an abbreviated three letter month name is only one extra character - the size argument for using numbers is usually bogus.

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    +1 In my opinion, it's also more natural to use a month name (or abbreviation). People rarely talk about being in the '5th month' rather than 'May'.
    – Brendon
    Commented May 21, 2013 at 8:27
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    YYYY-MM-DD also of course sorts chronologically using an alphabetical sort, which may or may not be useful
    – jk.
    Commented May 21, 2013 at 9:55
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    YYYY-MM-DD is actually the ISO standard. See en.wikipedia.org/wiki/ISO_8601 Commented May 21, 2013 at 12:52
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    Obligatory xkcd.com/1179 Commented May 21, 2013 at 13:02
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    @Brendon - actually, Japanese uses numbered months, instead of naming them. Commented May 21, 2013 at 16:03

Please see ISO 8601 (eg http://en.wikipedia.org/wiki/ISO_8601)

yyyy-mm-dd hh:mm:ss

First, this is simply the largest to the smallest unit. No other argument--no matter how tightly held--can seem to overcome this logic.

The 4-digit year removes any confusion as to what the other numbers represent--even when the hyphens are left out. (Use of a 2-digit year--in any order--cannot always establish anything.)

I discovered this dating schema decades ago looking at a Star Trek calendar and saw that stardates were yyyymm.dd (Note: I was looking at calendars--not Star Trek stuff.)

I am an American with a mild dyslexia. I saw (or perceived) just enough dates that were written "backwards" that I could and can never remember which order we are expected to presume they mean if the days (or years) are also 1-12. (I also eschew the " / " as these make the date look confusing.)

I use year-month-date both with and increasingly with out hyphens or spaces; and day, year month date where the day and the month are spelled out. This is by my choice--the ISO 8601 just gives me a fallback argument--in case I ever need one.

NOTE: Some software programs might use, eg, "mm" for minutes, "MM" for month in numbers, and "MMMM" for the month spelled out; "hh" might mean 12-hours and "HH" might mean 24-hours. All of these codes within their own software are subject to the whim of the programmer(s).

  • YYMMDD used to be unambiguous, up until about 13 years ago.
    – supercat
    Commented Jan 16, 2014 at 21:47
  • @supercat Depends on the domain. On an ancestry site, it was always ambiguous (but the right value could be inferred, same as now)
    – Izkata
    Commented May 4, 2015 at 16:08
  • @Izkata: Order ambiguity with YYMMDD would only be an issue if the earliest possible date was between January 1, 1900 and December 30, 1931. If the earliest date could go further than that, specifying the century would be appropriate in any case, in which case YYYYMMDD would be essentially unambiguous given that YYYYDDMM is never used. A date of the form 18xxyyzz, 19xxyyzz or 20xxyyzz, with yy being 12 or less, could only sensibly would be YYYYMMDD unless it represented a year prior to 1300.
    – supercat
    Commented May 4, 2015 at 16:36
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    @supercat I mentioned an ancestry site because the example I was thinking of was my great-grandfather being born in something like '97 (1897, not 1997). So the 1999/2000/2001 rollover isn't the only time when 2-digit years were ambiguous, but whether it's a valid thing to be concerned about depends on the project's range - like an ancestry site
    – Izkata
    Commented May 4, 2015 at 16:41

Perhaps start with the year first? You'll initially throw someone off, but for a good reason. I have never seen a YYYY-DD-MM structure in the wild, only YYYY-MM-DD. It would seem to follow for users that this may not be how they are used to seeing the date, but it does make the expectations clear. You could also locate a key nearby for any date format (if this is say, a chart of events).

  • YYYY-MM-DD is the format recommended by ISO 8601 and a XKCD 1179 (see other answers and comments). It's a possible solution, alright, but not the friendliest one.
    – Dvir Adler
    Commented May 23, 2013 at 15:13

Yes we do; hence the Public Service Announcement from xkcd on "... the correct way to write numeric dates".

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    When it comes to XKCD, I don't know if that's something that disturbs the general public, or maybe just the computer geeks, who can't stand the fact dates cannot be sorted alpha-numerically
    – Dvir Adler
    Commented May 28, 2013 at 4:54

You could adopt an internationally recognizable format of dd-MON-yyyy to avoid confusion, For example, see: http://www.oracle.com/webfolder/ux/middleware/richclient/index.html?/webfolder/ux/middleware/richclient/guidelines5/commonFormats.html

However I think if the site, portal or app is US Domestic market or business only, then a US format is reasonable to assume.

Alternatively you could add a notation on the screen advising that the dates are shown in a US format (and give an example).

Ideally, the UX should allow the users to enter the date format using what they're comfortable with and do an on-fly conversion and then store the date in a format that can be rendered back as per user preference. UX considerations should also enable the user to select their format even within a locale convention.

For example, Sunday, January 28, 2011. A shortened format can also be used, e.g, Jan-28-11 or Jan-28-2011. As a general rule if the viewing audience is international or likely to be then avoiding an all number display format would be safer, though that seems to be outside your use case, so 01-28-2011 would be acceptable.

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    How is this an international standard? Try guessing what date this is: 28-Фев-2012.
    – Pasha
    Commented May 22, 2013 at 0:14
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    @PashaS: The C language standard specifies that DATE will expand to a macro with the compilation date using the first three characters of the English-language names of the months, so at least among programmers those three-letter sequences should be recognizable. Incidentally, in some languages the month names are not unique in their first three characters (e.g. in French, the sixth and seventh months both start "Jui") but in English they are. Month abbreviations are also distinct from weekday ones, unlike in French (the third month shares three letters with a weekday).
    – supercat
    Commented May 22, 2013 at 4:22
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    In addition, I may not know which month that refers to, but I know which element in the date it represents.
    – Julian
    Commented May 22, 2013 at 8:22

The reason that Americans get confused with the date format is because they assume 01/02/2013 is 2 January 2013 in their format which is month day year, when in reality it is either 2 January 2013 (month day year) or 1 February 2013 (day month year). Year month day format is also confusing because the year is moved to the front. Americans are not used to talking like this. Example: “When is your birthday?” “Oh, my birthday is on the 2nd of April”. They will get it, but they are not used to it. They always talk like this. Example: “When is your birthday?” “Oh, it is on April 2nd”. When I see a numeric date, like 01/02/2013, I have to guess the format whether it is day month year or month day year. Overall use YYYY-MM-DD. Written on 29 May 2019 at 14:24 UTC/GMT (2019-05-29T14:24:00 +0000 UTC)


In Iran we have our calendar (Shamsi also known as Jalali Calendar) and we always use YYYY/MM/DD, we use this format for other calendars too (like Julian)

Other formats are really confusing for us, both European and American formats.

It doesn't make sense to me why some people use DD/MM/YYYY or MM/DD/YYYY as we tend to put larger units at the left side, like we do with decimal numbers.

When we use YYYY/MM/DD, it eases sorting and also calculating dates.

It seems the global standard systems should create a unique format to prevent confusing.

  • That is not what the question was about.
    – Nash
    Commented Apr 2, 2021 at 22:32

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