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
}  
--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 to : 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]);