This is a tracking category for CS1 citations with date-holding parameters where the date values do not comply with MOS:DATEFORMAT.

Help desk

Check date values in: |<param1>=, |<param2>=, ...

When Citation Style 1 and Citation Style 2 templates contain date-holding parameters, an automated test is done to see if the dates are real dates that comply with a subset of the date rules in Wikipedia's Manual of Style, specifically checking for violations of MOS:DATEFORMAT.

To resolve this error, ensure that the date is an actual date and that the date format follows the Wikipedia Manual of Style's guidance on dates in the named parameter. See examples of unacceptable dates and how to fix them, below. Or, some conceptual issues to look for:

• impossible dates (e.g., 29 February 2011)
• |access-date= must specify a day, not just a month or year.
• misplaced, incorrect, or extraneous punctuation
• extraneous text
• hyphens or slashes instead of en dashes in date ranges (en dashes are required)
• misspelling or improper capitalization (see MOS:ALLCAPS for more detail that is not in Wikipedia Manual of Style's guidance on dates)
• other unacceptable date formats listed in MOS:BADDATEFORMAT
• more than one date in a date-holding parameter
• Does not handle years before 100 AD, including BCE/BC dates. Try using parameter |orig-year= instead.

See Help: Citation Style 1 for information about limitations in the CS1 citation templates' handling of date formats. The MOS section on date ranges describes how to separate dates in a date range. Do not use  , –, or {{spaced ndash}} as these corrupt the metadata. To add an en dash, use the CharInsert edit tool or see Wikipedia:How to make dashes. A bot is often able to correct the separator, provided the overall format is unambiguous.

Future dates in |date= in CS1|2 citations are limited to current year + 1; that is, for 2016, citation dates in 2017 are acceptable but citation dates in 2018 and beyond are not.

Dates prior to 1582 are treated as Julian calendar dates. Dates from 1582 onward are treated as Gregorian calendar dates. The Julian calendar was used in some places until approximately 1923. Three Julian calendar dates in the overlap period, 29 February in the years 1700, 1800, and 1900, will cause this error message because those years are not leap years in the Gregorian calendar.

The access date (in |access-date=) is checked to ensure that it contains a full date (day, month, and year) and is between 15 January 2001 (the founding date of Wikipedia) and today's date plus one day, because it represents the date that an editor viewed a web-based source to verify a statement on Wikipedia. Because editors may be in time zones that are one day ahead of the UTC date, one extra day is accepted.

Pages with this error are automatically placed in Category:CS1 errors: dates.^[a]

While most of the Citation Style 1 and Citation Style 2 error messages are visible to all readers, some remain hidden. Editors who wish to see all of the CS1|2 error messages can do so by updating their common or skin CSS stylesheet to include:

.citation-comment {display: inline !important;} /* show all Citation Style 1 error messages */

Even with this css installed, older pages in Wikipedia's cache may not have been updated to show these error messages even though the page is listed in one of the tracking categories. A WP:NULLEDIT will resolve that issue.

Notes