Each user can choose in their preferences the date and time format used by MediaWiki when generating date and/or time, in page history, recent changes, etc.

The formats vary with the user's language. Options are made available for a language if listed in the $datePreferences array of its messages file (languages/messages/Messages*.php). The ID used in the list needs to be named in the $dateFormats array (whether the general one or the override in the Messages*.php file in question) and defined there with the appropriate sprintfDate() format; otherwise it will be ignored.

The options are then listed in Special:Preferences accordingly to the definitions, in the same order. They use January 15, 2001 as example. For English they are:

• default (No preference)
• mdy (16:12, January 15, 2001)
• dmy (16:12, 15 January 2001)
• ymd (16:12, 2001 January 15)
• numerical yyyy-mm-dd ( like ISO 8601, but without calendar conversions, and without implying that it is the date according to the Gregorian calendar)

• Help:Extension:ParserFunctions##time

• Manual:$wgAmericanDates