anchor_year, year = mw.ustring.match(date_string, patterns_t['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 -- 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 -- 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  
--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  
--year= for acceptable values:
YYY, YYYY, year-only ranges, their circa forms, with or without CITEREF disambiguators.  
When |year= holds some form of date that is not one of these year-only dates, emit a maintenance message.  
This function necessary because many non-cs1|2 templates have a |year= parameter so cirrus searches are more-or-
less useless  
local function year_check (year)
year = year:gsub ('c%. *', ''); -- remove circa annotation (if present) before testing <year>  
for _, index in ipairs ({'y-y', 'y4-y2', 'y'}) do -- spin through these indexes into patterns_t
if mw.ustring.match (year, patterns_t[index][1]) then
return; -- if a match then |year= holds a valid 'year'
end
end  
set_message ('maint_year'); -- if here, |year= value is not an accepted value; add a maint cat
end  
--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