Wikipedia:Overview of date formatting guidelines

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Wikipedia's guidelines for formatting dates (MOS:DATEFORMAT) set out the three date formats acceptable for use in Wikipedia articles, namely:

  • Day–month–year (DMY) format—e.g., 21 March 2020 or 21 Mar 2020;
  • Month–day–year (MDY) format—e.g., March 21, 2020 or Mar 21, 2020;
  • Year–month–day (YMD) format—e.g., 2020-03-21 (also called the "all-numeric" format; used only where space is limited, such as in references and some tables and infoboxes, but not in article text proper).

The appropriate format for a particular situation is determined by the (somewhat confusing) interaction between three sub-provisions of MOS:DATEFORMAT. The priority among these provisions can be summarised as follows:

  1. Consistency (MOS:DATEUNIFY): Each article should use either DMY or MDY consistently, except that in references, access/archive dates (and in some cases publication dates) may use YMD.
  2. Strong national ties to a topic (MOS:DATETIES): Articles on topics with strong ties to a particular English-speaking nation should generally use the date format most commonly used in that nation. This generally means:
    • articles on US topics use MDY, except articles on modern US military topics use DMY in line with modern military usage;
    • articles on Canadian topics may use either DMY or MDY;
    • articles on topics relating to other English-speaking countries use DMY.
There may be other exceptions for particular topic areas.
Note that MOS:DATETIES does not apply to topics related to non-English-speaking countries. For example, articles on French topics do not necessarily use DMY, even though DMY is the predominant format in France.
  1. Retaining existing format (MOS:DATERET): If an article has evolved using predominantly one format, don't change it except:
  • to conform with strong national ties (in accordance with MOS:DATETIES, as discussed in 2 above); or
  • for good reason, by consensus on the article's talk page (see below).
Think carefully before changing established date formats of existing articles, especially multiple articles in a particular subject area. Consider whether the proposed change would improve Wikipedia (beyond conforming the articles to your personal preference) and whether editors who have contributed to the article(s) may have reached a consensus to use a particular format. Other editors may feel justified in reverting date-format changes made without prior discussion, even when those changes are supported by the above guidelines.

As with any guidelines, occasional exceptions will apply. If there is good reason to diverge from the guidelines in the case of a particular article, use common sense and seek consensus on the article's talk page.