--[[--------------------------< F O R W A R D   D E C L A R A T I O N S >--------------------------------------

]]



local add_prop_cat, is_set, in_array, set_message, substitute, wrap_style;		-- imported functions from selected Module:Citation/CS1/Utilities

local cfg;																		-- table of tables imported from selected Module:Citation/CS1/Configuration





--[[--------------------------< F I L E - S C O P E   D E C L A R A T I O N S >--------------------------------



File-scope variables are declared here



]]



local lang_object = mw.getContentLanguage();									-- used by is_valid_accessdate(), is_valid_year(), date_name_xlate(); TODO: move to ~/Configuration?

local year_limit;																-- used by is_valid_year()





--[=[-------------------------< I S _ V A L I D _ A C C E S S D A T E >----------------------------------------



returns true if:

	Wikipedia start date <= accessdate < today + 2 days



Wikipedia start date is 2001-01-15T00:00:00 UTC which is 979516800 seconds after 1970-01-01T00:00:00 UTC (the start of Unix time)

accessdate is the date provided in |access-date= at time 00:00:00 UTC

today is the current date at time 00:00:00 UTC plus 48 hours

	if today is 2015-01-01T00:00:00 then

		adding 24 hours gives 2015-01-02T00:00:00 – one second more than today

		adding 24 hours gives 2015-01-03T00:00:00 – one second more than tomorrow



This function does not work if it is fed month names for languages other than English.  Wikimedia #time: parser

apparently doesn't understand non-English date month names. This function will always return false when the date

contains a non-English month name because good1 is false after the call to lang.formatDate().  To get around that

call this function with YYYY-MM-DD format dates.



]=]



local function is_valid_accessdate (accessdate)

	local good1, good2;

	local access_ts, tomorrow_ts;												-- to hold Unix time stamps representing the dates



	good1, access_ts = pcall (lang_object.formatDate, lang_object, 'U', accessdate );			-- convert accessdate value to Unix timestamp 

	good2, tomorrow_ts = pcall (lang_object.formatDate, lang_object, 'U', 'today + 2 days' );	-- today midnight + 2 days is one second more than all day tomorrow

	

	if good1 and good2 then														-- lang.formatDate() returns a timestamp in the local script which which tonumber() may not understand

		access_ts = tonumber (access_ts) or lang_object:parseFormattedNumber (access_ts);		-- convert to numbers for the comparison;

		tomorrow_ts = tonumber (tomorrow_ts) or lang_object:parseFormattedNumber (tomorrow_ts);

	else

		return false;															-- one or both failed to convert to Unix time stamp

	end



	if 979516800 <= access_ts and access_ts < tomorrow_ts then					-- Wikipedia start date <= accessdate < tomorrow's date

		return true;

	else

		return false;															-- accessdate out of range

	end

end





--[[--------------------------< G E T _ M O N T H _ N U M B E R >----------------------------------------------



returns a number according to the month in a date: 1 for January, etc.  Capitalization and spelling must be correct.

If not a valid month, returns 0



]]



local function get_month_number (month)

	return cfg.date_names'local'].longmonth or cfg.date_names'local'].shortmonth or	-- look for local names first

			cfg.date_names'en'].longmonth or	cfg.date_names'en'].shortmonth or		-- failing that, look for English names

			0;																				-- not a recognized month name

end





--[[--------------------------< G E T _ S E A S O N _ N U M B E R >--------------------------------------------



returns a number according to the sequence of seasons in a year: 21 for Spring, etc.  Capitalization and spelling

must be correct. If not a valid season, returns 0.

	21-24 = Spring, Summer, Autumn, Winter, independent of “Hemisphere”



returns 0 when <param> is not |date=



Season numbering is defined by Extended Date/Time Format (EDTF) specification (https://www.loc.gov/standards/datetime/)

which became part of ISO 8601 in 2019.  See '§Sub-year groupings'.  The standard defines various divisions using

numbers 21-41.  cs1|2 only supports generic seasons.  EDTF does support the distinction between north and south

hemisphere seasons but cs1|2 has no way to make that distinction.



These additional divisions not currently supported:

	25-28 = Spring - Northern Hemisphere, Summer- Northern Hemisphere, Autumn - Northern Hemisphere, Winter - Northern Hemisphere

	29-32 = Spring – Southern Hemisphere, Summer– Southern Hemisphere, Autumn – Southern Hemisphere, Winter - Southern Hemisphere

	33-36 = Quarter 1, Quarter 2, Quarter 3, Quarter 4 (3 months each)

	37-39 = Quadrimester 1, Quadrimester 2, Quadrimester 3 (4 months each)

	40-41 = Semestral 1, Semestral-2 (6 months each)



]]



local function get_season_number (season, param)

	if 'date' ~= param then

		return 0;																-- season dates only supported by |date=

	end

	return cfg.date_names'local'].seasonseason or							-- look for local names first

			cfg.date_names'en'].seasonseason or								-- failing that, look for English names

			0;																	-- not a recognized season name

end





--[[--------------------------< G E T _ Q U A R T E R _ N U M B E R >------------------------------------------



returns a number according to the sequence of quarters in a year: 33 for first quarter, etc.  Capitalization and spelling

must be correct. If not a valid quarter, returns 0.

	33-36 = Quarter 1, Quarter 2, Quarter 3, Quarter 4 (3 months each)



returns 0 when <param> is not |date=



Quarter numbering is defined by Extended Date/Time Format (EDTF) specification (https://www.loc.gov/standards/datetime/)

which became part of ISO 8601 in 2019.  See '§Sub-year groupings'.  The standard defines various divisions using

numbers 21-41.  cs1|2 only supports generic seasons and quarters.



These additional divisions not currently supported:

	37-39 = Quadrimester 1, Quadrimester 2, Quadrimester 3 (4 months each)

	40-41 = Semestral 1, Semestral-2 (6 months each)



]]



local function get_quarter_number (quarter, param)

	if 'date' ~= param then

		return 0;																-- quarter dates only supported by |date=

	end

	quarter = mw.ustring.gsub (quarter, ' +', ' ');								-- special case replace multiple space chars with a single space char

	return cfg.date_names'local'].quarterquarter or							-- look for local names first

			cfg.date_names'en'].quarterquarter or							-- failing that, look for English names

			0;																	-- not a recognized quarter name

end





--[[--------------------------< G E T _ P R O P E R _ N A M E _ N U M B E R >----------------------------------



returns a non-zero number if date contains a recognized proper-name.  Capitalization and spelling must be correct.



returns 0 when <param> is not |date=



]]



local function get_proper_name_number (name, param)

	if 'date' ~= param then

		return 0;																-- proper-name dates only supported by |date=

	end

	return cfg.date_names'local'].namedname or								-- look for local names dates first

			cfg.date_names'en'].namedname or									-- failing that, look for English names

			0;																	-- not a recognized named date

end





--[[--------------------------< G E T _ E L E M E N T _ N U M B E R <------------------------------------------



returns true if month or season or quarter or proper name is valid (properly spelled, capitalized, abbreviated)



]]



local function get_element_number (element, param)

	local num;

	

	local funcs = {get_month_number, get_season_number, get_quarter_number, get_proper_name_number};	-- list of functions to execute in order

	

	for _, func in ipairs (funcs) do											-- spin through the function list

		num = func (element, param);											-- call the function and get the returned number

		if 0 ~= num then														-- non-zero when valid month season quarter 

			return num;															-- return that number

		end

	end

	return nil;																	-- not valid

end





--[[--------------------------< I S _ V A L I D _ Y E A R >----------------------------------------------------



Function gets current year from the server and compares it to year from a citation parameter.  Years more than one

year in the future are not acceptable.



Special case for |pmc-embargo-date=: years more than two years in the future are not acceptable



]]



local function is_valid_year (year, param)

	if not is_set (year_limit) then

		year_limit = tonumber(os.date("%Y"))+1;									-- global variable so we only have to fetch it once

	end



	year = tonumber (year) or lang_object:parseFormattedNumber (year);			-- convert to number for the comparison

	if year and (100 > year) then												-- years less than 100 not supported

		return false;

	end

	

	if 'pmc-embargo-date' == param then											-- special case for |pmc-embargo-date=

		return year and (year <= tonumber(os.date("%Y"))+2) or false;			-- years more than two years in the future are not accepted

	end	

	return year and (year <= year_limit) or false;

end





--[[--------------------------< I S _ V A L I D _ D A T E >----------------------------------------------------



Returns true if day is less than or equal to the number of days in month and year is no farther into the future

than next year; else returns false.



Assumes Julian calendar prior to year 1582 and Gregorian calendar thereafter. Accounts for Julian calendar leap

years before 1582 and Gregorian leap years after 1582. Where the two calendars overlap (1582 to approximately

1923) dates are assumed to be Gregorian.



]]



local function is_valid_date (year, month, day, param)

local days_in_month = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

local month_length;

	if not is_valid_year (year, param) then										-- no farther into the future than next year except |pmc-embargo-date= no more than two years in the future

		return false;

	end

	

	month = tonumber (month);													-- required for YYYY-MM-DD dates

	

	if (2 == month) then														-- if February

		month_length = 28;														-- then 28 days unless

		if 1582 > tonumber(year) then											-- Julian calendar

			if 0 == (year%4) then												-- is a leap year?

				month_length = 29;												-- if leap year then 29 days in February

			end

		else																	-- Gregorian calendar

			if (0 == (year%4) and (0 ~= (year%100) or 0 == (year%400))) then	-- is a leap year?

				month_length = 29;												-- if leap year then 29 days in February

			end

		end

	else

		month_length = days_in_monthmonth];

	end



	if tonumber (day) > month_length then

		return false;

	end

	return true;

end





--[[--------------------------< I S _ V A L I D _ M O N T H _ R A N G E _ S T Y L E >--------------------------



Months in a range are expected to have the same style: Jan–Mar or October–December but not February–Mar or Jul–August. 

This function looks in cfg.date_names{} to see if both month names are listed in the long subtable or both are

listed in the short subtable.  When both have the same style (both are listed in the same table), returns true; false else



]]



local function is_valid_month_range_style (month1, month2)

	if (cfg.date_names.en.longmonth1 and cfg.date_names.en.longmonth2]) or					-- are both English names listed in the long subtable?

		(cfg.date_names.en.shortmonth1 and cfg.date_names.en.shortmonth2]) or				-- are both English names listed in the short subtable?

		(cfg.date_names'local'].longmonth1 and cfg.date_names'local'].longmonth2]) or		-- are both local names listed in the long subtable?

		(cfg.date_names'local'].shortmonth1 and cfg.date_names'local'].shortmonth2]) then	-- are both local names listed in the short subtable?

			return true;

	end

	return false;																-- names are mixed

end





--[[--------------------------< I S _ V A L I D _ M O N T H _ S E A S O N _ R A N G E >------------------------



Check a pair of months or seasons to see if both are valid members of a month or season pair.



Month pairs are expected to be left to right, earliest to latest in time.



All season ranges are accepted as valid because there are publishers out there who have published a Summer–Spring YYYY issue, hence treat as ok



]]



local function is_valid_month_season_range(range_start, range_end, param)

	local range_start_number = get_month_number (range_start);

	local range_end_number;



	if 0 == range_start_number then												-- is this a month range?

		range_start_number = get_season_number (range_start, param);			-- not a month; is it a season? get start season number

		range_end_number = get_season_number (range_end, param);				-- get end season number



		if (0 ~= range_start_number) and (0 ~= range_end_number) and (range_start_number ~= range_end_number) then

			return true;														-- any season pairing is accepted except when both are the same

		end

		return false;															-- range_start and/or range_end is not a season

	end

																				-- here when range_start is a month

	range_end_number = get_month_number (range_end);							-- get end month number

	if range_start_number < range_end_number and								-- range_start is a month; does range_start precede range_end?

		is_valid_month_range_style (range_start, range_end) then				-- do months have the same style?

			return true;														-- proper order and same style

	end

	return false;																-- range_start month number is greater than or equal to range end number; or range end isn't a month

end





--[[--------------------------< M A K E _ C O I N S _ D A T E >------------------------------------------------



This function receives a table of date parts for one or two dates and an empty table reference declared in

Module:Citation/CS1.  The function is called only for |date= parameters and only if the |date=<value> is 

determined to be a valid date format.  The question of what to do with invalid date formats is not answered here.



The date parts in the input table are converted to an ISO 8601 conforming date string:

	single whole dates:		yyyy-mm-dd

	month and year dates:	yyyy-mm

	year dates:				yyyy

	ranges:					yyyy-mm-dd/yyyy-mm-dd

							yyyy-mm/yyyy-mm

							yyyy/yyyy



Dates in the Julian calendar are reduced to year or year/year so that we don't have to do calendar conversion from

Julian to Proleptic Gregorian.



The input table has:

	year, year2 – always present; if before 1582, ignore months and days if present

	month, month2 – 0 if not provided, 1-12 for months, 21-24 for seasons; 99 Christmas

	day, day2 –  0 if not provided, 1-31 for days

	

the output table receives:

	rftdate:	an ISO 8601 formatted date

	rftchron:	a free-form version of the date, usually without year which is in rftdate (season ranges and proper-name dates)

	rftssn:		one of four season keywords: winter, spring, summer, fall (lowercase)

	rftquarter:	one of four values: 1, 2, 3, 4



]]



local function make_COinS_date (input, tCOinS_date)

	local date;																	-- one date or first date in a range

	local date2 = '';															-- end of range date

	input.year = tonumber (input.year) or lang_object:parseFormattedNumber (input.year);	-- language-aware tonumber()

	input.year2 = tonumber (input.year2) or lang_object:parseFormattedNumber (input.year2);	-- COinS dates are pseudo-ISO 8601 so convert to Arabic numerals



	if ((1582 == input.year) and (10 > tonumber(input.month))) or (1582 > input.year) then	-- if a Julian calendar date

		tCOinS_date.rftdate = tostring (input.year);							-- &rft.date gets year only

		return;																	-- done

	end

																				-- here for all forms of Gregorian dates

	if 20 < tonumber (input.month) then											-- if season, quarter, or proper-name date

		date = input.year;														-- &rft.date gets year only

		if 0 ~= input.year2 and input.year ~= input.year2 then					-- if a range, only the second year portion when not the same as range start year

			date = string.format ('%.4d/%.4d', input.year, input.year2)			-- assemble the date range

		end



		local season = {[24 = 'winter', 21 = 'spring', 22 = 'summer', 23 = 'fall', 33 = '1', 34 = '2', 35 = '3', 36 = '4', 98 = 'Easter', 99 = 'Christmas'};	-- seasons lowercase, no autumn; proper-names use title case

		if 0 == input.month2 then												-- single season, quarter, or proper-name date

			if 40 < tonumber(input.month) then

				tCOinS_date.rftchron = seasoninput.month];						-- proper-name date; used in journal metadata only

			elseif 30 < tonumber(input.month) then

				tCOinS_date.rftquarter = seasoninput.month];					-- quarter date; used in journal metadata only

			else

				tCOinS_date.rftssn = seasoninput.month];						-- season date; used in journal metadata only

			end

		else																	-- season ranges are lumped into &rft.chron; &rft.ssn and &rft.quarter are left blank

			if input.year ~= input.year2 then									-- season year – season year range or season year–year

				if 0 ~= input.month2 then

					tCOinS_date.rftchron = string.format ('%s %s – %s %s', seasoninput.month], input.year, seasoninput.month2], input.year2);	-- used in journal metadata only

				end

			else																-- season–season year range

				tCOinS_date.rftchron = seasoninput.month .. '–' .. seasoninput.month2];	-- season–season year range; used in journal metadata only

			end

		end



		tCOinS_date.rftdate = tostring (date);

		return;																	-- done

	end

																				-- here for gregorian calendar dates

	if 0 ~= input.day then

		date = string.format ('%s-%.2d-%.2d', input.year, tonumber(input.month), tonumber(input.day));	-- whole date

	elseif 0 ~= input.month then

		date = string.format ('%s-%.2d', input.year, tonumber(input.month));	-- year and month

	else

		date = string.format ('%s', input.year);								-- just year

	end



	if 0 ~= input.year2 then

		if 0 ~= input.day2 then

			date2 = string.format ('/%s-%.2d-%.2d', input.year2, tonumber(input.month2), tonumber(input.day2));		-- whole date

		elseif 0 ~= input.month2 then

			date2 = string.format ('/%s-%.2d', input.year2, tonumber(input.month2));	-- year and month

		else

			date2 = string.format ('/%s', input.year2);							-- just year

		end

	end

	

	tCOinS_date.rftdate = date .. date2;										-- date2 has the '/' separator

	return;

end





--[[--------------------------< P A T T E R N S >--------------------------------------------------------------



this is the list of patterns for date formats that this module recognizes.  Approximately the first half of these

patterns represent formats that might be reformatted into another format.  Those that might be reformatted have

'indicator' letters that identify the content of the matching capture: 'd' (day), 'm' (month), 'a' (anchor year),

'y' (year); second day, month, year have a '2' suffix.



These patterns are used for both date validation and for reformatting.  This table should not be moved to ~/Configuration

because changes to this table require changes to check_date() and to reformatter() and reformat_date()



]]



local patterns = {

	 																			-- year-initial numerical year-month-day

	'ymd' = {'^(%d%d%d%d)%-(%d%d)%-(%d%d)$', 'y', 'm', 'd'},					

																				-- month-initial: month day, year

	'Mdy' = {'^(%D-) +([1-9]%d?), +((%d%d%d%d?)%a?)$', 'm', 'd', 'a', 'y'},

																				-- month-initial day range: month day–day, year; days are separated by endash

	'Md-dy' = {'^(%D-) +([1-9]%d?)[%-–]([1-9]%d?), +((%d%d%d%d)%a?)$', 'm', 'd', 'd2', 'a', 'y'},

																				-- day-initial: day month year

	'dMy' = {'^([1-9]%d?) +(%D-) +((%d%d%d%d?)%a?)$', 'd', 'm', 'a', 'y'},

																				-- year-initial: year month day; day: 1 or 2 two digits, leading zero allowed; not supported at en.wiki

	--	['yMd'] = {'^((%d%d%d%d?)%a?) +(%D-) +(%d%d?)$', 'a', 'y', 'm', 'd'},

																				-- day-range-initial: day–day month year; days are separated by endash

	'd-dMy' = {'^([1-9]%d?)[%-–]([1-9]%d?) +(%D-) +((%d%d%d%d)%a?)$', 'd', 'd2', 'm', 'a', 'y'},

																				-- day initial month-day-range: day month - day month year; uses spaced endash

	'dM-dMy' = {'^([1-9]%d?) +(%D-) +[%-–] +([1-9]%d?) +(%D-) +((%d%d%d%d)%a?)$', 'd', 'm', 'd2', 'm2', 'a', 'y'},

																				-- month initial month-day-range: month day – month day, year;  uses spaced endash

	'Md-Mdy' = {'^(%D-) +([1-9]%d?) +[%-–] +(%D-) +([1-9]%d?), +((%d%d%d%d)%a?)$','m', 'd', 'm2', 'd2', 'a', 'y'},

																				-- day initial month-day-year-range: day month year - day month year; uses spaced endash

	'dMy-dMy' = {'^([1-9]%d?) +(%D-) +(%d%d%d%d) +[%-–] +([1-9]%d?) +(%D-) +((%d%d%d%d)%a?)$', 'd', 'm', 'y', 'd2', 'm2', 'a', 'y2'},

																				-- month initial month-day-year-range: month day, year – month day, year;  uses spaced endash

	'Mdy-Mdy' = {'^(%D-) +([1-9]%d?), +(%d%d%d%d) +[%-–] +(%D-) +([1-9]%d?), +((%d%d%d%d)%a?)$', 'm', 'd', 'y', 'm2', 'd2', 'a', 'y2'},



																				-- these date formats cannot be converted, per se, but month name can be rendered short or long

																				-- month/season year - month/season year; separated by spaced endash

	'My-My' = {'^(%D-) +(%d%d%d%d) +[%-–] +(%D-) +((%d%d%d%d)%a?)$', 'm', 'y', 'm2', 'a', 'y2'},

																				-- month/season range year; months separated by endash

	'M-My' = {'^(%D-)[%-–](%D-) +((%d%d%d%d)%a?)$', 'm', 'm2', 'a', 'y'},

																				-- month/season year or proper-name year; quarter year when First Quarter YYYY etc.

	'My' = {'^([^%d–]-) +((%d%d%d%d)%a?)$', 'm', 'a', 'y'},					-- this way because endash is a member of %D; %D- will match January–March 2019 when it shouldn't



																				-- these date formats cannot be converted

	'Sy4-y2' = {'^(%D-) +((%d%d)%d%d)[%-–]((%d%d)%a?)$'},						-- special case Winter/Summer year-year (YYYY-YY); year separated with unspaced endash

	'Sy-y' = {'^(%D-) +(%d%d%d%d)[%-–]((%d%d%d%d)%a?)$'},						-- special case Winter/Summer year-year; year separated with unspaced endash

	'y-y' = {'^(%d%d%d%d?)[%-–]((%d%d%d%d?)%a?)$'},							-- year range: YYY-YYY or YYY-YYYY or YYYY–YYYY; separated by unspaced endash; 100-9999

	'y4-y2' = {'^((%d%d)%d%d)[%-–]((%d%d)%a?)$'},								-- year range: YYYY–YY; separated by unspaced endash

	'y' = {'^((%d%d%d%d?)%a?)$'},												-- year; here accept either YYY or YYYY

	}





--[[--------------------------< I S _ V A L I D _ E M B A R G O _ D A T E >------------------------------------



returns true and date value if that value has proper dmy, mdy, ymd format.



returns false and 9999 (embargoed forever) when date value is not proper format; assumes that when |pmc-embargo-date= is

set, the editor intended to embargo a PMC but |pmc-embargo-date= does not hold a single date.



]]



local function is_valid_embargo_date (v)

	if v:match (patterns'ymd'][1]) or											-- ymd

		v:match (patterns'Mdy'][1]) or											-- dmy

		v:match (patterns'dMy'][1]) then										-- mdy

			return true, v;

	end

	return false, '9999';														-- if here not good date so return false and set embargo date to long time in future

end





--[[--------------------------< C H E C K _ D A T E >----------------------------------------------------------



Check date format to see that it is one of the formats approved by WP:DATESNO or WP:DATERANGE. Exception: only

allowed range separator is endash.  Additionally, check the date to see that it is a real date: no 31 in 30-day

months; no 29 February when not a leap year.  Months, both long-form and three character abbreviations, and seasons

must be spelled correctly.  Future years beyond next year are not allowed.



If the date fails the format tests, this function returns false and does not return values for anchor_year and

COinS_date.  When this happens, the date parameter is (DEBUG: not?) used in the COinS metadata and the CITEREF identifier gets

its year from the year parameter if present otherwise CITEREF does not get a date value.



Inputs:

	date_string - date string from date-holding parameters (date, year, publication-date, access-date, pmc-embargo-date, archive-date, lay-date)



Returns:

	false if date string is not a real date; else

	true, anchor_year, COinS_date

		anchor_year can be used in CITEREF anchors

		COinS_date is ISO 8601 format date; see make_COInS_date()



]]



local function check_date (date_string, param, tCOinS_date)

	local year;																	-- assume that year2, months, and days are not used;

	local year2 = 0;															-- second year in a year range

	local month = 0;

	local month2 = 0;															-- second month in a month range

	local day = 0;

	local day2 = 0;																-- second day in a day range

	local anchor_year;

	local coins_date;



	if date_string:match (patterns'ymd'][1]) then								-- year-initial numerical year month day format

		year, month, day = date_string:match (patterns'ymd'][1]);

		if 12 < tonumber(month) or 1 > tonumber(month) or 1582 > tonumber(year) or 0 == tonumber(day) then return false; end	-- month or day number not valid or not Gregorian calendar

		anchor_year = year;

	

	elseif mw.ustring.match(date_string, patterns'Mdy'][1]) then				-- month-initial: month day, year

		month, day, anchor_year, year = mw.ustring.match(date_string, patterns'Mdy'][1]);

		month = get_month_number (month);

		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months

				

	elseif mw.ustring.match(date_string, patterns'Md-dy'][1]) then				-- month-initial day range: month day–day, year; days are separated by endash

		month, day, day2, anchor_year, year = mw.ustring.match(date_string, patterns'Md-dy'][1]);

		if tonumber(day) >= tonumber(day2) then return false; end				-- date range order is left to right: earlier to later; dates may not be the same;

		month = get_month_number (month);

		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months

		month2=month;															-- for metadata

		year2 = year;



	elseif mw.ustring.match(date_string, patterns'dMy'][1]) then				-- day-initial: day month year

		day, month, anchor_year, year = mw.ustring.match(date_string, patterns'dMy'][1]);

		month = get_month_number (month);

		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months



--[[ NOT supported at en.wiki

	elseif mw.ustring.match(date_string, patterns['yMd'][1]) then				-- year-initial: year month day; day: 1 or 2 two digits, leading zero allowed

		anchor_year, year, month, day = mw.ustring.match(date_string, patterns['yMd'][1]);

		month = get_month_number (month);

		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months

-- end NOT supported at en.wiki ]]



	elseif mw.ustring.match(date_string, patterns'd-dMy'][1]) then				-- day-range-initial: day–day month year; days are separated by endash

		day, day2, month, anchor_year, year = mw.ustring.match(date_string, patterns'd-dMy'][1]);

		if tonumber(day) >= tonumber(day2) then return false; end				-- date range order is left to right: earlier to later; dates may not be the same;

		month = get_month_number (month);

		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months

		month2 = month;															-- for metadata

		year2 = year;



	elseif mw.ustring.match(date_string, patterns'dM-dMy'][1]) then			-- day initial month-day-range: day month - day month year; uses spaced endash

		day, month, day2, month2, anchor_year, year = mw.ustring.match(date_string, patterns'dM-dMy'][1]);

		if (not is_valid_month_season_range(month, month2)) or not is_valid_year(year) then return false; end	-- date range order is left to right: earlier to later;

		month = get_month_number (month);										-- for metadata

		month2 = get_month_number (month2);

		year2 = year;



	elseif mw.ustring.match(date_string, patterns'Md-Mdy'][1]) then			-- month initial month-day-range: month day – month day, year; uses spaced endash

		month, day, month2, day2, anchor_year, year = mw.ustring.match(date_string, patterns'Md-Mdy'][1]);

		if (not is_valid_month_season_range(month, month2, param)) or not is_valid_year(year) then return false; end

		month = get_month_number (month);										-- for metadata

		month2 = get_month_number (month2);

		year2 = year;



	elseif mw.ustring.match(date_string, patterns'dMy-dMy'][1]) then			-- day initial month-day-year-range: day month year - day month year; uses spaced endash

		day, month, year, day2, month2, anchor_year, year2 = mw.ustring.match(date_string, patterns'dMy-dMy'][1]);

		if tonumber(year2) <= tonumber(year) then return false; end				-- must be sequential years, left to right, earlier to later

		if not is_valid_year(year2) or not is_valid_month_range_style(month, month2) then return false; end		-- year2 no more than one year in the future; months same style

		month = get_month_number (month);										-- for metadata

		month2 = get_month_number (month2);

		if 0 == month or 0 == month2 then return false; end						-- both must be valid



	elseif mw.ustring.match(date_string, patterns'Mdy-Mdy'][1]) then			-- month initial month-day-year-range: month day, year – month day, year; uses spaced endash

		month, day, year, month2, day2, anchor_year, year2 = mw.ustring.match(date_string, patterns'Mdy-Mdy'][1]);

		if tonumber(year2) <= tonumber(year) then return false; end				-- must be sequential years, left to right, earlier to later

		if not is_valid_year(year2) or not is_valid_month_range_style(month, month2) then return false; end		-- year2 no more than one year in the future; months same style

		month = get_month_number (month);										-- for metadata

		month2 = get_month_number(month2);

		if 0 == month or 0 == month2 then return false; end						-- both must be valid



	elseif mw.ustring.match(date_string, patterns'Sy4-y2'][1]) then			-- special case Winter/Summer year-year (YYYY-YY); year separated with unspaced endash

		local century;

		month, year, century, anchor_year, year2 = mw.ustring.match(date_string, patterns'Sy4-y2'][1]);

		if 'Winter' ~= month and 'Summer' ~= month then return false end;		-- 'month' can only be Winter or Summer

		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor_year from both years

		year2 = century..year2;													-- add the century to year2 for comparisons

		if 1 ~= tonumber(year2) - tonumber(year) then return false; end			-- must be sequential years, left to right, earlier to later

		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year

		month = get_season_number(month, param);



	elseif mw.ustring.match(date_string, patterns'Sy-y'][1]) then				-- special case Winter/Summer year-year; year separated with unspaced endash

		month, year, anchor_year, year2 = mw.ustring.match(date_string, patterns'Sy-y'][1]);

		month = get_season_number (month, param);								-- <month> can only be winter or summer; also for metadata

		if (month ~= cfg.date_names'en'].season'Winter']) and (month ~= cfg.date_names'en'].season'Summer']) then

			return false;														-- not Summer or Winter; abandon

		end

		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor_year from both years

		if 1 ~= tonumber(year2) - tonumber(year) then return false; end			-- must be sequential years, left to right, earlier to later

		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year



	elseif mw.ustring.match(date_string, patterns'My-My'][1]) then				-- month/season year - month/season year; separated by spaced endash

		month, year, month2, anchor_year, year2 = mw.ustring.match(date_string, patterns'My-My'][1]);

		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor_year from both years

		if tonumber(year) >= tonumber(year2) then return false; end				-- left to right, earlier to later, not the same

		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year

		if 0 ~= get_month_number(month) and 0 ~= get_month_number(month2) and is_valid_month_range_style(month, month2) then 	-- both must be month year, same month style

			month = get_month_number(month);

			month2 = get_month_number(month2);

		elseif 0 ~= get_season_number(month, param) and 0 ~= get_season_number(month2, param) then	-- both must be season year, not mixed

			month = get_season_number(month, param);

			month2 = get_season_number(month2, param);

		else

			 return false;

		end



	elseif mw.ustring.match(date_string, patterns'M-My'][1]) then				-- month/season range year; months separated by endash 

		month, month2, anchor_year, year = mw.ustring.match(date_string, patterns'M-My'][1]);

		if (not is_valid_month_season_range(month, month2, param)) or (not is_valid_year(year)) then return false; end

		if 0 ~= get_month_number(month) then									-- determined to be a valid range so just check this one to know if month or season

			month = get_month_number(month);

			month2 = get_month_number(month2);

			if 0 == month or 0 == month2 then return false; end

		else

			month = get_season_number(month, param);

			month2 = get_season_number(month2, param);

		end

		year2 = year;

		

	elseif mw.ustring.match(date_string, patterns'My'][1]) then				-- month/season/quarter/proper-name year

		month, anchor_year, year = mw.ustring.match(date_string, patterns'My'][1]);

		if not is_valid_year(year) then return false; end

		month = get_element_number(month, param);								-- get month season quarter proper-name number or nil

		if not month then return false; end										-- not valid whatever it is



	elseif mw.ustring.match(date_string, patterns'y-y'][1]) then				-- Year range: YYY-YYY or YYY-YYYY or YYYY–YYYY; separated by unspaced endash; 100-9999

		year, anchor_year, year2 = mw.ustring.match(date_string, patterns'y-y'][1]);

		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor year from both years

		if tonumber(year) >= tonumber(year2) then return false; end				-- left to right, earlier to later, not the same

		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year



	elseif mw.ustring.match(date_string, patterns'y4-y2'][1]) then				-- Year range: YYYY–YY; separated by unspaced endash

		local century;

		year, century, anchor_year, year2 = mw.ustring.match(date_string, patterns'y4-y2'][1]);

		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor year from both years



		if 13 > tonumber(year2) then return false; end							-- don't allow 2003-05 which might be May 2003

		year2 = century .. year2;												-- add the century to year2 for comparisons

		if tonumber(year) >= tonumber(year2) then return false; end				-- left to right, earlier to later, not the same

		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year



		if in_array (param, {'date', 'publication-date', 'year'}) then			-- here when 'valid' abbreviated year range; if one of these parameters

			add_prop_cat ('year-range-abbreviated');							-- add properties cat

		end



	elseif mw.ustring.match(date_string, patterns'y'][1]) then					-- year; here accept either YYY or YYYY

		anchor_year, year = mw.ustring.match(date_string, patterns'y'][1]);

		if false == is_valid_year(year) then

			return false;

		end



	else

		return false;															-- date format not one of the MOS:DATE approved formats

	end



	if param ~= 'date' then														-- CITEREF disambiguation only allowed in |date=; |year= & |publication-date= promote to date

		if anchor_year:match ('%l$') then

			return false;

		end

	end



	if 'access-date' == param then												-- test access-date here because we have numerical date parts

		if 0 ~= year and 0 ~= month and 0 ~= day and 							-- all parts of a single date required

			0 == year2 and 0 == month2 and 0 == day2 then						-- none of these; access-date must not be a range

				if not is_valid_accessdate(year .. '-' .. month .. '-' .. day) then	

					return false;												-- return false when access-date out of bounds

				end

		else

			return false;														-- return false when access-date is a range of two dates

		end

	end



	if 'archive-date' == param then												-- test archive-date here because we have numerical date parts

		if not (0 ~= year and 0 ~= month and 0 ~= day and						-- all parts of a single date required

			0 == year2 and 0 == month2 and 0 == day2) then						-- none of these; archive-date must not be a range

				return false;													-- return false when archive-date is a range of two dates

		end

	end



	local result=true;															-- check whole dates for validity; assume true because not all dates will go through this test

	if 0 ~= year and 0 ~= month and 0 ~= day and 0 == year2 and 0 == month2 and 0 == day2 then		-- YMD (simple whole date)

		result = is_valid_date (year, month, day, param);						-- <param> for |pmc-embargo-date=



	elseif 0 ~= year and 0 ~= month and 0 ~= day and 0 == year2 and 0 == month2 and 0 ~= day2 then	-- YMD-d (day range)

		result = is_valid_date (year, month, day);

		result = result and is_valid_date (year, month, day2);



	elseif 0 ~= year and 0 ~= month and 0 ~= day and 0 == year2 and 0 ~= month2 and 0 ~= day2 then	-- YMD-md (day month range)

		result = is_valid_date (year, month, day);

		result = result and is_valid_date (year, month2, day2);



	elseif 0 ~= year and 0 ~= month and 0 ~= day and 0 ~= year2 and 0 ~= month2 and 0 ~= day2 then	-- YMD-ymd (day month year range)

		result = is_valid_date(year, month, day);

		result = result and is_valid_date(year2, month2, day2);

	end

	

	if false == result then return false; end



	if nil ~= tCOinS_date then													-- this table only passed into this function when testing |date= parameter values

		make_COinS_date ({year = year, month = month, day = day, year2 = year2, month2 = month2, day2 = day2}, tCOinS_date);	-- make an ISO 8601 date string for COinS

	end

	

	return true, anchor_year;													-- format is good and date string represents a real date

end	





--[[--------------------------< D A T E S >--------------------------------------------------------------------



Cycle the date-holding parameters in passed table date_parameters_list through check_date() to check compliance with MOS:DATE. For all valid dates, check_date() returns

true. The |date= parameter test is unique, it is the only date holding parameter from which values for anchor_year (used in CITEREF identifiers) and COinS_date (used in

the COinS metadata) are derived.  The |date= parameter is the only date-holding parameter that is allowed to contain the no-date keywords "n.d." or "nd" (without quotes).



Unlike most error messages created in this module, only one error message is created by this function. Because all of the date holding parameters are processed serially,

parameters with errors are added to the <error_list> sequence table as the dates are tested.



]]



local function dates(date_parameters_list, tCOinS_date, error_list)

	local anchor_year;															-- will return as nil if the date being tested is not |date=

	local COinS_date;															-- will return as nil if the date being tested is not |date=

	local embargo_date;															-- if embargo date is a good dmy, mdy, ymd date then holds original value else reset to 9999

	local good_date = false;



	for k, v in pairs(date_parameters_list) do									-- for each date-holding parameter in the list

		if is_set(v.val) then													-- if the parameter has a value

			v.val = mw.ustring.gsub(v.val, '%d', cfg.date_names.local_digits);	-- translate 'local' digits to Western 0-9

			if v.val:match("^c%. [1-9]%d%d%d?%a?$") then						-- special case for c. year or with or without CITEREF disambiguator - only |date= and |year=

				local year = v.val:match("c%. ([1-9]%d%d%d?)%a?");				-- get the year portion so it can be tested

				if 'date' == k then

					anchor_year, COinS_date = v.val:match("((c%. [1-9]%d%d%d?)%a?)");	-- anchor year and COinS_date only from |date= parameter

					good_date = is_valid_year(year);

				elseif 'year' == k then

					good_date = is_valid_year(year);

				end

			elseif 'date' == k then												-- if the parameter is |date=

				if v.val:match("^n%.d%.%a?$") then -- ToDo: I18N								-- if |date=n.d. with or without a CITEREF disambiguator

					good_date, anchor_year, COinS_date = true, v.val:match("((n%.d%.)%a?)"); -- ToDo: I18N	-- "n.d."; no error when date parameter is set to no date

				elseif v.val:match("^nd%a?$") then -- ToDo: I18N								-- if |date=nd with or without a CITEREF disambiguator

					good_date, anchor_year, COinS_date = true, v.val:match("((nd)%a?)"); -- ToDo: I18N	-- "nd";	no error when date parameter is set to no date

				else

					good_date, anchor_year, COinS_date = check_date (v.val, k, tCOinS_date);	-- go test the date

				end

			elseif 'year' == k then												-- if the parameter is |year= it should hold only a year value

				if v.val:match("^[1-9]%d%d%d?%a?$") then						-- if |year = 3 or 4 digits only with or without a CITEREF disambiguator

					good_date, anchor_year, COinS_date = true, v.val:match("((%d+)%a?)");

				end

			elseif 'pmc-embargo-date' == k then									-- if the parameter is |pmc-embargo-date=

				good_date = check_date (v.val, k);								-- go test the date

				if true == good_date then										-- if the date is a valid date

					good_date, embargo_date = is_valid_embargo_date (v.val);	-- is |pmc-embargo-date= date a single dmy, mdy, or ymd formatted date? yes: returns embargo date; no: returns 9999

				end

			else																-- any other date-holding parameter

				good_date = check_date (v.val, k);								-- go test the date

			end

			if false == good_date then											-- assemble one error message so we don't add the tracking category multiple times

				table.insert (error_list, wrap_style ('parameter', v.name));	-- make parameter name suitable for error message list

			end

		end

	end

	return anchor_year, embargo_date;											-- and done

end





--[[--------------------------< Y E A R _ D A T E _ C H E C K >------------------------------------------------



Compare the value provided in |year= with the year value(s) provided in |date=.  This function sets a local numeric value:

	0 - year value does not match the year value in date

	1 - (default) year value matches the year value in date or one of the year values when date contains two years

	2 - year value matches the year value in date when date is in the form YYYY-MM-DD and year is disambiguated (|year=YYYYx)



the numeric value in <result> determines the 'output' if any from this function:

	0 – adds error message to error_list sequence table

	1 – adds maint cat

	2 – does nothing



]]



local function year_date_check (year_string, year_origin, date_string, date_origin, error_list)

	local year;

	local date1;

	local date2;

	local result = 1;															-- result of the test; assume that the test passes



	year = year_string:match ('(%d%d%d%d?)');



	if date_string:match ('%d%d%d%d%-%d%d%-%d%d') and year_string:match ('%d%d%d%d%a') then	--special case where both date and year are required YYYY-MM-DD and YYYYx

		date1 = date_string:match ('(%d%d%d%d)');

		year = year_string:match ('(%d%d%d%d)');

		if year ~= date1 then

			result = 0;															-- years don't match

		else

			result = 2;															-- years match; but because disambiguated, don't add to maint cat

		end

		

	elseif date_string:match ("%d%d%d%d?.-%d%d%d%d?") then						-- any of the standard range formats of date with two three- or four-digit years

		date1, date2 = date_string:match ("(%d%d%d%d?).-(%d%d%d%d?)");

		if year ~= date1 and year ~= date2 then

			result = 0;

		end



	elseif mw.ustring.match(date_string, "%d%d%d%d[%-–]%d%d") then				-- YYYY-YY date ranges

		local century;

		date1, century, date2 = mw.ustring.match(date_string, "((%d%d)%d%d)[%-–]+(%d%d)");

		date2 = century..date2;													-- convert YY to YYYY

		if year ~= date1 and year ~= date2 then

			result = 0;

		end



	elseif date_string:match ("%d%d%d%d?") then									-- any of the standard formats of date with one year

		date1 = date_string:match ("(%d%d%d%d?)");

		if year ~= date1 then

			result = 0;

		end

	else																		-- should never get here; this function called only when no other date errors

		result = 0;																-- no recognizable year in date

	end



	if 0 == result then															-- year / date mismatch

		table.insert (error_list, substitute (cfg.messages'mismatch'], {year_origin, date_origin}));	-- add error message to error_list sequence table

	elseif 1 == result then														-- redundant year / date

		set_message ('maint_date_year');										-- add a maint cat

	end

end





--[[--------------------------< R E F O R M A T T E R >--------------------------------------------------------



reformat 'date' into new format specified by format_param if pattern_idx (the current format of 'date') can be

reformatted.  Does the grunt work for reformat_dates().



The table re_formats maps pattern_idx (current format) and format_param (desired format) to a table that holds:

	format string used by string.format()

	identifier letters ('d', 'm', 'y', 'd2', 'm2', 'y2') that serve as indexes into a table t{} that holds captures

		from mw.ustring.match() for the various date parts specified by  patterns[pattern_idx][1]



Items in patterns{} have the general form:

	['ymd'] = {'^(%d%d%d%d)%-(%d%d)%-(%d%d)$', 'y', 'm', 'd'}, where:

		['ymd'] is pattern_idx

		patterns['ymd'][1] is the match pattern with captures for mw.ustring.match()

		patterns['ymd'][2] is an indicator letter identifying the content of the first capture

		patterns['ymd'][3] ... the second capture etc.



when a pattern matches a date, the captures are loaded into table t{} in capture order using the idemtifier

characters as indexes into t{}  For the above, a ymd date is in t{} as:

	t.y = first capture (year), t.m = second capture (month), t.d = third capture (day)



To reformat, this function is called with the pattern_idx that matches the current format of the date and with

format_param set to the desired format.  This function loads table t{} as described and then calls string.format()

with the format string specified by re_format[pattern_idx][format_param][1] using values taken from t{} according

to the capture identifier letters specified by patterns[pattern_idx][format_param][n] where n is 2..



]]



local re_formats = {

	'ymd' = {																	-- date format is ymd; reformat to:

		'mdy' = {'%s %s, %s', 'm', 'd', 'y'},									-- |df=mdy

		'dmy' = {'%s %s %s', 'd', 'm', 'y'},									-- |df=dmy

	--		['yMd'] = {'%s %s %s', 'y', 'm', 'd'},								-- |df=yMd; not supported at en.wiki

		},

	'Mdy' = {																	-- date format is Mdy; reformat to:

		'mdy' = {'%s %s, %s', 'm', 'd', 'y'},									-- for long/short reformatting

		'dmy' = {'%s %s %s', 'd', 'm', 'y'},									-- |df=dmy

		'ymd' = {'%s-%s-%s', 'y', 'm', 'd'},									-- |df=ymd

	--		['yMd'] = {'%s %s %s', 'y', 'm', 'd'},								-- |df=yMd; not supported at en.wiki

		},

	'dMy' = {																	-- date format is dMy; reformat to:

		'dmy' = {'%s %s %s', 'd', 'm', 'y'},									-- for long/short reformatting

		'mdy' = {'%s %s, %s', 'm', 'd', 'y'},									-- |df=mdy

		'ymd' = {'%s-%s-%s', 'y', 'm', 'd'},									-- |df=ymd

	--		['yMd'] = {'%s %s %s', 'y', 'm', 'd'},								-- |df=yMd; not supported at en.wiki

		},

	'Md-dy' = {																-- date format is Md-dy; reformat to:

		'mdy' = {'%s %s–%s, %s', 'm', 'd', 'd2', 'y'},						-- for long/short reformatting

		'dmy' = {'%s–%s %s %s', 'd', 'd2', 'm', 'y'},							-- |df=dmy -> d-dMy 

		},

	'd-dMy' = {																-- date format is d-d>y; reformat to:

		'dmy' = {'%s–%s %s %s', 'd', 'd2', 'm', 'y'},							-- for long/short reformatting

		'mdy' = {'%s %s–%s, %s', 'm', 'd', 'd2', 'y'},						-- |df=mdy -> Md-dy 

		},

	'dM-dMy' = {																-- date format is dM-dMy; reformat to:

		'dmy' = {'%s %s – %s %s %s', 'd', 'm', 'd2', 'm2', 'y'},				-- for long/short reformatting

		'mdy' = {'%s %s – %s %s, %s', 'm', 'd', 'm2', 'd2', 'y'},				-- |df=mdy -> Md-Mdy 

		},

	'Md-Mdy' = {																-- date format is Md-Mdy; reformat to:

		'mdy' = {'%s %s – %s %s, %s', 'm', 'd',  'm2', 'd2', 'y'},			-- for long/short reformatting

		'dmy' = {'%s %s – %s %s %s', 'd', 'm', 'd2', 'm2', 'y'},				-- |df=dmy -> dM-dMy 

		},

	'dMy-dMy' = {																-- date format is dMy-dMy; reformat to:

		'dmy' = {'%s %s %s – %s %s %s', 'd', 'm', 'y', 'd2', 'm2', 'y2'},		-- for long/short reformatting

		'mdy' = {'%s %s, %s – %s %s, %s', 'm', 'd', 'y', 'm2', 'd2', 'y2'},	-- |df=mdy -> Mdy-Mdy 

		},

	'Mdy-Mdy' = {																-- date format is Mdy-Mdy; reformat to:

		'mdy' = {'%s %s, %s – %s %s, %s', 'm', 'd', 'y', 'm2', 'd2', 'y2'},	-- for long/short reformatting

		'dmy' = {'%s %s %s – %s %s %s', 'd', 'm', 'y', 'd2', 'm2', 'y2'},		-- |df=dmy -> dMy-dMy 

		},

	'My-My' = {																-- these for long/short reformatting

		'any' = {'%s %s – %s %s', 'm', 'y', 'm2', 'y2'},						-- dmy/mdy agnostic

		},

	'M-My' = {																-- these for long/short reformatting

		'any' = {'%s–%s %s', 'm', 'm2', 'y'},									-- dmy/mdy agnostic

		},

	'My' = {																	-- these for long/short reformatting

		'any' = {'%s %s', 'm', 'y'},											-- dmy/mdy agnostic

		},

	--	['yMd'] = {																-- not supported at en.wiki

	--		['mdy'] = {'%s %s, %s', 'm', 'd', 'y'},								-- |df=mdy

	--		['dmy'] = {'%s %s %s', 'd', 'm', 'y'},								-- |df=dmy

	--		['ymd'] = {'%s-%s-%s', 'y', 'm', 'd'},								-- |df=ymd

	--		},

	}





local function reformatter (date, pattern_idx, format_param, mon_len)

	if not in_array (pattern_idx, {'ymd', 'Mdy', 'Md-dy', 'dMy', 'yMd', 'd-dMy', 'dM-dMy', 'Md-Mdy', 'dMy-dMy', 'Mdy-Mdy', 'My-My', 'M-My', 'My'}) then

		return;																	-- not in this set of date format patterns then not a reformattable date

	end

	

	if 'ymd' == format_param and in_array (pattern_idx, {'ymd', 'Md-dy', 'd-dMy', 'dM-dMy', 'Md-Mdy', 'dMy-dMy', 'Mdy-Mdy', 'My-My', 'M-My', 'My'}) then

		return;																	-- ymd date ranges not supported at en.wiki; no point in reformatting ymd to ymd

	end



	if in_array (pattern_idx, {'My', 'M-My', 'My-My'}) then						-- these are not dmy/mdy so can't be 'reformatted' into either

		format_param = 'any';													-- so format-agnostic 

	end



																				-- yMd is not supported at en.wiki; when yMd is supported at your wiki, uncomment the next line

	--	if 'yMd' == format_param and in_array (pattern_idx, {'yMd', 'Md-dy', 'd-dMy', 'dM-dMy', 'Md-Mdy', 'dMy-dMy', 'Mdy-Mdy'}) then	-- these formats not convertable; yMd not supported at en.wiki

	if 'yMd' == format_param then												-- yMd not supported at en.wiki; when yMd is supported at your wiki, remove or comment-out this line

		return;																	-- not a reformattable date

	end

	

	local c1, c2, c3, c4, c5, c6, c7;											-- these hold the captures specified in patterns[pattern_idx][1]

	c1, c2, c3, c4, c5, c6, c7 = mw.ustring.match (date, patternspattern_idx][1]);	-- get the captures



	local t = {																	-- table that holds k/v pairs of date parts from the captures and patterns[pattern_idx][2..]

		patternspattern_idx][2]] = c1;										-- at minimum there is always one capture with a matching indicator letter

		patternspattern_idx][3 or 'x' = c2;									-- patterns can have a variable number of captures; each capture requires an indicator letter;

		patternspattern_idx][4 or 'x' = c3;									-- where there is no capture, there is no indicator letter so n in patterns[pattern_idx][n] will be nil;

		patternspattern_idx][5 or 'x' = c4;									-- the 'x' here spoofs an indicator letter to prevent 'table index is nil' error

		patternspattern_idx][6 or 'x' = c5;

		patternspattern_idx][7 or 'x' = c6;

		patternspattern_idx][8 or 'x' = c7;

		};



	if t.a then																	-- if this date has an anchor year capture (all convertable date formats except ymd)

		if t.y2 then															-- for year range date formats														

			t.y2 = t.a;															-- use the anchor year capture when reassembling the date

		else																	-- here for single date formats (except ymd)

			t.y = t.a;															-- use the anchor year capture when reassembling the date

		end

	end



	if tonumber(t.m) then														-- if raw month is a number (converting from ymd)

		if 's' == mon_len then													-- if we are to use abbreviated month names

			t.m = cfg.date_names'inv_local_short'][tonumber(t.m)];					-- convert it to a month name

		else

			t.m = cfg.date_names'inv_local_long'][tonumber(t.m)];					-- convert it to a month name

		end

		t.d = t.d:gsub ('0(%d)', '%1');											-- strip leading '0' from day if present

	elseif 'ymd' == format_param then											-- when converting to ymd

		t.y = t.y:gsub ('%a', '');												-- strip CITREF disambiguator if present; anchor year already known so process can proceed; TODO: maint message?

		if 1582 > tonumber (t.y) then											-- ymd format dates not allowed before 1582

			return;

		end

		t.m = string.format ('%02d', get_month_number (t.m));					-- make sure that month and day are two digits

		t.d = string.format ('%02d', t.d);

	elseif mon_len then															-- if mon_len is set to either 'short' or 'long'

		for _, mon in ipairs ({'m', 'm2'}) do									-- because there can be two month names, check both 

			if tmon then

				tmon = get_month_number (tmon]);								-- get the month number for this month (is length agnostic)

				if 0 == tmon then return; end									-- seasons and named dates can't be converted

				tmon = (('s' == mon_len) and cfg.date_names'inv_local_short'][tmon]]) or cfg.date_names'inv_local_long'][tmon]];	-- fetch month name according to length

			end

		end

	end



	local new_date = string.format (re_formatspattern_idx][format_param][1],	-- format string

		tre_formatspattern_idx][format_param][2]],							-- named captures from t{}

		tre_formatspattern_idx][format_param][3]],

		tre_formatspattern_idx][format_param][4]],

		tre_formatspattern_idx][format_param][5]],

		tre_formatspattern_idx][format_param][6]],

		tre_formatspattern_idx][format_param][7]],

		tre_formatspattern_idx][format_param][8]]

		);



	return new_date;

end





--[[-------------------------< R E F O R M A T _ D A T E S >--------------------------------------------------



Reformats existing dates into the format specified by format.



format is one of several manual keywords: dmy, dmy-all, mdy, mdy-all, ymd, ymd-all.  The -all version includes

access- and archive-dates; otherwise these dates are not reformatted.



This function allows automatic date formatting.  In ~/Configuration, the article source is searched for one of

the {{use xxx dates}} templates.  If found, xxx becomes the global date format as xxx-all.  If |cs1-dates= in

{{use xxx dates}} has legitimate value then that value determines how cs1|2 dates will be rendered.  Legitimate

values for |cs1-dates= are:

	l - all dates are rendered with long month names

	ls - publication dates use long month names; access-/archive-dates use abbreviated month names

	ly - publication dates use long month names; access-/archive-dates rendered in ymd format

	s - all dates are rendered with abbreviated (short) month names

	sy - publication dates use abbreviated month names; access-/archive-dates rendered in ymd format

	y - all dates are rendered in ymd format



the format argument for automatic date formatting will be the format specified by {{use xxx dates}} with the

value supplied by |cs1-dates so one of: xxx-l, xxx-ls, xxx-ly, xxx-s, xxx-sy, xxx-y, or simply xxx (|cs1-dates=

empty, omitted, or invalid) where xxx shall be either of dmy or mdy.



dates are extracted from date_parameters_list, reformatted (if appropriate), and then written back into the

list in the new format.  Dates in date_parameters_list are presumed here to be valid (no errors).  This function

returns true when a date has been reformatted, false else.  Actual reformatting is done by reformatter().



]]



local function reformat_dates (date_parameters_list, format)

	local all = false;															-- set to false to skip access- and archive-dates

	local len_p = 'l';															-- default publication date length shall be long

	local len_a = 'l';															-- default access-/archive-date length shall be long

	local result = false;

	local new_date;																

	

	if format:match('%a+%-all') then											-- manual df keyword; auto df keyword when length not specified in {{use xxx dates}}; 

		format = format:match('(%a+)%-all');									-- extract the format

		all = true;																-- all dates are long format dates because this keyword doesn't specify length

	elseif format:match('%a+%-[lsy][sy]?') then									-- auto df keywords; internal only

		all = true;																-- auto df applies to all dates; use length specified by capture len_p for all dates

		format, len_p, len_a = format:match('(%a+)%-([lsy])([sy]?)');			-- extract the format and length keywords

		if 'y' == len_p then													-- because allowed by MOS:DATEUNIFY (sort of) range dates and My dates not reformatted

			format = 'ymd';														-- override {{use xxx dates}}

		elseif (not is_set(len_a)) or (len_p == len_a) then						-- no access-/archive-date length specified or same length as publication dates then

			len_a = len_p;														-- in case len_a not set

		end

	end																			-- else only publication dates and they are long



	for param_name, param_val in pairs (date_parameters_list) do				-- for each date-holding parameter in the list

		if is_set (param_val.val) then											-- if the parameter has a value

			if not (not all and in_array (param_name, {'access-date', 'archive-date'})) then	-- skip access- or archive-date unless format is xxx-all; yeah, ugly; TODO: find a better way

				for pattern_idx, pattern in pairs (patterns) do

					if mw.ustring.match (param_val.val, pattern1]) then

						if all and in_array (param_name, {'access-date', 'archive-date'}) then	-- if this date is an access- or archive-date

							new_date = reformatter (param_val.val, pattern_idx, (('y' == len_a) and 'ymd') or format, len_a);	-- choose ymd or dmy/mdy according to len_a setting

						else													-- all other dates

							new_date = reformatter (param_val.val, pattern_idx, format, len_p);

						end

						

						if new_date then										-- set when date was reformatted

							date_parameters_listparam_name].val = new_date;	-- update date in date list

							result = true;										-- and announce that changes have been made

							break;

						end

					end	-- if

				end		-- for

			end			-- if

		end				-- if

	end					-- for

	return result;																-- declare boolean result and done

end





--[[--------------------------< D A T E _ H Y P H E N _ T O _ D A S H >----------------------------------------



Loops through the list of date-holding parameters and converts any hyphen to an ndash.  Not called if the cs1|2

template has any date errors.



Modifies the date_parameters_list and returns true if hyphens are replaced, else returns false.



]]



local function date_hyphen_to_dash (date_parameters_list)

	local result = false;

	local n;

	for param_name, param_val in pairs(date_parameters_list) do					-- for each date-holding parameter in the list

		if is_set (param_val.val) and

			not mw.ustring.match (param_val.val, patterns.ymd1]) then			-- for those that are not ymd dates (ustring because here digits may not be Western)

				param_val.val, n = param_val.val:gsub ('%-', '–');				-- replace any hyphen with ndash

				if 0 ~= n then

					date_parameters_listparam_name].val = param_val.val;		-- update the list

					result = true;

				end

		end

	end

	return result;																-- so we know if any hyphens were replaced

end





--[[-------------------------< D A T E _ N A M E _ X L A T E >------------------------------------------------



Attempts to translate English date names to local-language date names using names supplied by MediaWiki's

date parser function.  This is simple name-for-name replacement and may not work for all languages.



if xlat_dig is true, this function will also translate Western (English) digits to the local language's digits.

This will also translate ymd dates.



]]



local function date_name_xlate (date_parameters_list, xlt_dig)

	local xlate;

	local mode;																	-- long or short month names

	local modified = false;

	local date;

	

	local sources_t = {

		{cfg.date_names.en.long, cfg.date_names.inv_local_long},				-- for translating long English month names to long local month names

		{cfg.date_names.en.short, cfg.date_names.inv_local_short},				-- short month names

		{cfg.date_names.en.quarter, cfg.date_names.inv_local_quarter},			-- quarter date names

		{cfg.date_names.en.season, cfg.date_names.inv_local_season},			-- season date nam

		{cfg.date_names.en.named, cfg.date_names.inv_local_named},				-- named dates

		}



	local function is_xlateable (month)											-- local function to get local date name that replaces existing English-language date name

		for _, date_names_t in ipairs (sources_t) do							-- for each sequence table in date_names_t

			if date_names_t1][month then										-- if date name is English month (long or short), quarter, season or named and

				if date_names_t2][date_names_t1][month]] then					-- if there is a matching local date name

					return date_names_t2][date_names_t1][month]];				-- return the local date name

				end

			end

		end

	end



	for param_name, param_val in pairs(date_parameters_list) do					-- for each date-holding parameter in the list

		if is_set(param_val.val) then											-- if the parameter has a value

			date = param_val.val;

			for month in mw.ustring.gmatch (date, '[%a ]+') do					-- iterate through all date names in the date (single date or date range)

				month = mw.text.trim (month);									-- this because quarterly dates contain whitespace

				xlate = is_xlateable (month);									-- get translate <month>; returns translation or nil

				

				if xlate then		

					date = mw.ustring.gsub (date, month, xlate);				-- replace the English with the translation

					date_parameters_listparam_name].val = date;				-- save the translated date

					modified = true;

				end

			end



			if xlt_dig then														-- shall we also translate digits?

				date = date:gsub ('%d', cfg.date_names.xlate_digits);			-- translate digits from Western to 'local digits'

				date_parameters_listparam_name].val = date;					-- save the translated date

				modified = true;

			end

		end

	end

	

	return modified;

end





--[[--------------------------< S E T _ S E L E C T E D _ M O D U L E S >--------------------------------------



Sets local imported functions table to same (live or sandbox) as that used by the other modules.



]]



local function set_selected_modules (cfg_table_ptr, utilities_page_ptr)

	add_prop_cat = utilities_page_ptr.add_prop_cat ;							-- import functions from selected Module:Citation/CS1/Utilities module

	is_set = utilities_page_ptr.is_set;

	in_array = utilities_page_ptr.in_array;

	set_message = utilities_page_ptr.set_message;

	substitute = utilities_page_ptr.substitute;

	wrap_style = utilities_page_ptr.wrap_style;



	cfg = cfg_table_ptr;														-- import tables from selected Module:Citation/CS1/Configuration

end





--[[--------------------------< A R C H I V E _ D A T E _ C H E C K >------------------------------------------



Compare value in |archive-date= with the timestamp in Wayback machine urls.  Emits an error message with suggested

date from the |archive-url= timestamp in an appropriate format when the value in |archive-date= does not match

the timestamp.



this function never called when any date in a cs1|2 template has errors



error message suggests new |archive-date= value in an appropriate format specified by <df>.  <df> is either 

|df= or cfg.global_df in that order.  If <df> is nil, suggested date has format from |archive-date=.  There is

a caveat: when |df=dmy or |df=mdy, the reformatter leaves |access-date= and |archive-date= formats as they are.

The error message suggested date is passed to the formatter as YYYY-MM-DD so when |df=dmy or |df=mdy, the format

is not changed.



]]



local function archive_date_check (archive_date, archive_url_timestamp, df)

	local archive_date_format = 'dmy-y';										-- holds the date format of date in |archive-date; default to ymd; 'dmy' used here to spoof reformat_dates() 

	

	for _, v_t in ipairs ({{'dMy', 'dmy-all'}, {'Mdy', 'mdy-all'}}) do			-- is |archive-date= format dmy or mdy?

		if archive_date:match (patternsv_t1]][1]) then						-- does the pattern match?

			archive_date_format = cfg.keywords_xlatev_t2]];					-- get appropriate |df= supported keyword from the i18n translator table

			break;

		end

	end

	

	local dates_t = {};

	dates_t'archive-date' = {val=archive_date, name=''};						-- setup to call reformat_dates(); never called when errors so <name> unset as not needed

	reformat_dates (dates_t, 'dmy-y');											-- reformat |archive-date= to ymd; 'dmy' used here to spoof reformat_dates()

	local archive_url_date = archive_url_timestamp:gsub ('(%d%d%d%d)(%d%d)(%d%d)%d*', '%1-%2-%3');	-- make ymd format date from timestamp



	if dates_t'archive-date'].val == archive_url_date then						-- are the two dates the same

		return;																	-- yes, done

	else

		dates_t'archive-date' = {val=archive_url_date, name=''};				-- setup to call reformat_dates() with the timestamp date

		reformat_dates (dates_t, df or archive_date_format);					-- reformat timestamp to format specified by <df> or format used in |archive-date= 

		archive_url_date = dates_t'archive-date'].val;

		set_message ('err_archive_date_url_ts_mismatch', archive_url_date);		-- emit an error message

	end

end





--[[--------------------------< E X P O R T E D   F U N C T I O N S >------------------------------------------

]]



return {																		-- return exported functions

	archive_date_check = archive_date_check,

	date_hyphen_to_dash = date_hyphen_to_dash,

	date_name_xlate = date_name_xlate,

	dates = dates,

	reformat_dates = reformat_dates,

	set_selected_modules = set_selected_modules,

	year_date_check = year_date_check,

	}