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 Wikipedia's Manual of Style, specifically MOS:BADDATEFORMAT.

To resolve this error, ensure that the date is an actual date and that the date format follows the Wikipedia Manual of Style in the named parameter. Some things to look for:

• misplaced, incorrect, or extraneous punctuation
• extraneous text
• incomplete year-initial dates
• hyphens instead of en dashes
• misspelling or improper capitalization (see MOS:ALLCAPS for more detail that is not in the above-linked Dates section)
• date formats listed in MOS:BADDATEFORMAT
• impossible dates (e.g., 29 February 2011)
• errors in |date= caused by errors in |year= or |month=
• more than one date in a date-holding parameter

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 is between 15 January 2001 (the founding date of Wikipedia) and today's date plus one day (currently 10 March 2016 UTC), 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