Template:Date table sorting/doc

Date table sorting is used to correctly sort and display dates in a sortable table (see Help:Sortable tables).

What it solves
Dates in their customary formats, if simply treated as alphanumeric text strings, sort in nonsensical ways: Use of the YYYY-MM-DD format would solve this problem, but with minor exceptions that format is not used in articles (see WP:DATEFORMAT).
 * 1 September 1998 sorts alphanumerically before 5 March 1967, because 1 is less than 5;
 * February 5, 1922 sorts alphanumerically before January 3, 1922, because F comes before J.

This template automatically attaches a "hidden key" to dates, causing them to sort correctly while still being displayed in one of the customary display formats such as February 5, 1922, or 5 Feb 1922.

Formatting
Using  produces a format that depends on, but is not necessarily equal to the format of the supplied date. The  parameter can take nine values.

Abbreviation
There are two ways of abbreviating the month name.
 * 1) Directly input an abbreviated month name.
 * 2) Use the   parameter. It can be placed before or after the date in the template. This allows one to abbreviate the month later if the table becomes too wide. It is easy to use find-and-replace in a text editor, or the wikitext editor, to replace   with

Additional sort key
In case two dates in a table are identical they may be ordered using the  parameter.

Wrapping
Wrapping of the date can help narrow a column and table. To allow wrapping use the  parameter. For further narrowing use the  parameter as described elsewhere. Both of these parameters help with wide tables, narrow screens, cell phones, etc..

TemplateData
{	"params": { "1": {			"label": "Full date or year", "description": "Full date if second to fourth parameters are not specfied, otherwise year. Full date can be either in \"YYYY-MM-DD\", \"DD-MM-YYYY\", \"DD Month YYYY\", \"Month DD, YYYY\", \"YYYY-MM\", \"DD Month\", \"Month DD\", \"Month YYYY\" or \"Month\" format. Year is either a positive number or a negative number. If fourth parameter is not specified negative numbers are interpreted as years of BC era. Parameter is optional if the second parameter is specified.", "example": "\"1893\", \"-89\", \"-10000\", \"Oct\", \"February 1767\", \"12 Aug 1987\", \"July 1, 1867\", \"25 October\", \"Jan 1\", \"2014-12-09\"", "required": true, "type": "string" },		"2": {			"label": "Month", "description": "Full or abbreviated month name or alternatively, a month number which can be zero-padded. Parameter is optional if the third parameter is not specified.", "example": "February, Feb, 2 or 02", "type": "string" },		"3": {			"label": "Day", "description": "Day, optionally zero-padded", "example": "7 or 07", "type": "number" },		"4": {			"label": "Era", "description": "BC, AD, BCE or CE. Takes effect only if the first parameter is a positive number.", "type": "string" },		"format": { "label": "Format", "description": "Controls the output format. Can be \"dmy\", \"dm\", \"mdy\", \"md\", \"my\", \"d\", \"m\", \"y\" or \"hide\".", "type": "string" },		"abbr": { "label": "Abbreviation", "description": "Abbreviates the month name", "example": "on", "type": "string", "default": "off" },		"addkey": { "label": "Additional sort key", "description": "Adds another sort key to resolve conflicts between rows with the same date", "example": "3", "type": "number" },		"nowrap": { "label": "Wrapping", "description": "To allow wrapping use the nowrap=off parameter.", "example": "off", "type": "boolean", "default": "on" }	},	"description": "Date table sorting is used to correctly sort and display dates in a sortable table." }

Sorting for incomplete dates

 * Whole months or years: A whole year or month (and year) is sorted according to its first day.
 * Missing years: If the year is not specified, the date will be sorted as if the year were the current year.
 * Blank dates: For no date input at all, the maximum possible sort key is used, so the entry will sort last.

Error handling
Errors are tracked in Category:Date table sorting templates with errors.

Calendar choice
The template is not capable of distinguishing Julian and Gregorian calendar dates. Also, it is not capable of taking a date in one calendar as input and outputting a date in the other calendar. Thus, to insure proper sorting, editors must either use one calendar for all dates, or pick a specific changeover date (for example, deciding that 4 October 1582 is Julian and all later dates are Gregorian); this would be done on an article-by article basis. Editors are also responsible for explaining to the reader whether the visible dates are Julian or Gregorian, if there is any possibility of confusion.

Linking
The template formerly linked dates automatically, with  used to suppress linking. In accordance with current guidelines, linking of dates is no longer supported and instances of  should be removed.