-- Date functions for use by other modules. -- I18N and time zones are not supported.  local MINUS = '−'  -- Unicode U+2212 MINUS SIGN local floor = math.floor  local Date, DateDiff, diffmt  -- forward declarations local uniq = { 'unique identifier' }  local function is_date(t) 	-- The system used to make a date read-only means there is no unique 	-- metatable that is conveniently accessible to check. 	return type(t) == 'table' and t._id == uniq end  local function is_diff(t) 	return type(t) == 'table' and getmetatable(t) == diffmt end  local function _list_join(list, sep) 	return table.concat(list, sep) end  local function collection() 	-- Return a table to hold items. 	return { 		n = 0, 		add = function (self, item) 			self.n = self.n + 1 			self[self.n] = item 		end, 		join = _list_join, 	} end  local function strip_to_nil(text) 	-- If text is a string, return its trimmed content, or nil if empty. 	-- Otherwise return text (convenient when Date fields are provided from 	-- another module which may pass a string, a number, or another type). 	if type(text) == 'string' then 		text = text:match('(%S.-)%s*$') 	end 	return text end  local function is_leap_year(year, calname) 	-- Return true if year is a leap year. 	if calname == 'Julian' then 		return year % 4 == 0 	end 	return (year % 4 == 0 and year % 100 ~= 0) or year % 400 == 0 end  local function days_in_month(year, month, calname) 	-- Return number of days (1..31) in given month (1..12). 	if month == 2 and is_leap_year(year, calname) then 		return 29 	end 	return ({ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 })[month] end  local function h_m_s(time) 	-- Return hour, minute, second extracted from fraction of a day. 	time = floor(time * 24 * 3600 + 0.5)  -- number of seconds 	local second = time % 60 	time = floor(time / 60) 	return floor(time / 60), time % 60, second end  local function hms(date) 	-- Return fraction of a day from date's time, where (0 <= fraction < 1) 	-- if the values are valid, but could be anything if outside range. 	return (date.hour + (date.minute + date.second / 60) / 60) / 24 end  local function julian_date(date) 	-- Return jd, jdz from a Julian or Gregorian calendar date where 	--   jd = Julian date and its fractional part is zero at noon 	--   jdz = same, but assume time is 00:00:00 if no time given 	-- http://www.tondering.dk/claus/cal/julperiod.php#formula 	-- Testing shows this works for all dates from year -9999 to 9999! 	-- JDN 0 is the 24-hour period starting at noon UTC on Monday 	--    1 January 4713 BC  = (-4712, 1, 1)   Julian calendar 	--   24 November 4714 BC = (-4713, 11, 24) Gregorian calendar 	local offset 	local a = floor((14 - date.month)/12) 	local y = date.year + 4800 - a 	if date.calendar == 'Julian' then 		offset = floor(y/4) - 32083 	else 		offset = floor(y/4) - floor(y/100) + floor(y/400) - 32045 	end 	local m = date.month + 12*a - 3 	local jd = date.day + floor((153*m + 2)/5) + 365*y + offset 	if date.hastime then 		jd = jd + hms(date) - 0.5 		return jd, jd 	end 	return jd, jd - 0.5 end  local function set_date_from_jd(date) 	-- Set the fields of table date from its Julian date field. 	-- Return true if date is valid. 	-- http://www.tondering.dk/claus/cal/julperiod.php#formula 	-- This handles the proleptic Julian and Gregorian calendars. 	-- Negative Julian dates are not defined but they work. 	local calname = date.calendar 	local low, high  -- min/max limits for date ranges −9999-01-01 to 9999-12-31 	if calname == 'Gregorian' then 		low, high = -1930999.5, 5373484.49999 	elseif calname == 'Julian' then 		low, high = -1931076.5, 5373557.49999 	else 		return 	end 	local jd = date.jd 	if not (type(jd) == 'number' and low <= jd and jd <= high) then 		return 	end 	local jdn = floor(jd) 	if date.hastime then 		local time = jd - jdn  -- 0 <= time < 1 		if time >= 0.5 then    -- if at or after midnight of next day 			jdn = jdn + 1 			time = time - 0.5 		else 			time = time + 0.5 		end 		date.hour, date.minute, date.second = h_m_s(time) 	else 		date.second = 0 		date.minute = 0 		date.hour = 0 	end 	local b, c 	if calname == 'Julian' then 		b = 0 		c = jdn + 32082 	else  -- Gregorian 		local a = jdn + 32044 		b = floor((4*a + 3)/146097) 		c = a - floor(146097*b/4) 	end 	local d = floor((4*c + 3)/1461) 	local e = c - floor(1461*d/4) 	local m = floor((5*e + 2)/153) 	date.day = e - floor((153*m + 2)/5) + 1 	date.month = m + 3 - 12*floor(m/10) 	date.year = 100*b + d - 4800 + floor(m/10) 	return true end  local function fix_numbers(numbers, y, m, d, H, M, S, partial, hastime, calendar) 	-- Put the result of normalizing the given values in table numbers. 	-- The result will have valid m, d values if y is valid; caller checks y. 	-- The logic of PHP mktime is followed where m or d can be zero to mean 	-- the previous unit, and -1 is the one before that, etc. 	-- Positive values carry forward. 	local date 	if not (1 <= m and m <= 12) then 		date = Date(y, 1, 1) 		if not date then return end 		date = date + ((m - 1) .. 'm') 		y, m = date.year, date.month 	end 	local days_hms 	if not partial then 		if hastime and H and M and S then 			if not (0 <= H and H <= 23 and 					0 <= M and M <= 59 and 					0 <= S and S <= 59) then 				days_hms = hms({ hour = H, minute = M, second = S }) 			end 		end 		if days_hms or not (1 <= d and d <= days_in_month(y, m, calendar)) then 			date = date or Date(y, m, 1) 			if not date then return end 			date = date + (d - 1 + (days_hms or 0)) 			y, m, d = date.year, date.month, date.day 			if days_hms then 				H, M, S = date.hour, date.minute, date.second 			end 		end 	end 	numbers.year = y 	numbers.month = m 	numbers.day = d 	if days_hms then 		-- Don't set H unless it was valid because a valid H will set hastime. 		numbers.hour = H 		numbers.minute = M 		numbers.second = S 	end end  local function set_date_from_numbers(date, numbers, options) 	-- Set the fields of table date from numeric values. 	-- Return true if date is valid. 	if type(numbers) ~= 'table' then 		return 	end 	local y = numbers.year   or date.year 	local m = numbers.month  or date.month 	local d = numbers.day    or date.day 	local H = numbers.hour 	local M = numbers.minute or date.minute or 0 	local S = numbers.second or date.second or 0 	local need_fix 	if y and m and d then 		date.partial = nil 		if not (-9999 <= y and y <= 9999 and 			1 <= m and m <= 12 and 			1 <= d and d <= days_in_month(y, m, date.calendar)) then 				if not date.want_fix then 					return 				end 				need_fix = true 		end 	elseif y and date.partial then 		if d or not (-9999 <= y and y <= 9999) then 			return 		end 		if m and not (1 <= m and m <= 12) then 			if not date.want_fix then 				return 			end 			need_fix = true 		end 	else 		return 	end 	if date.partial then 		H = nil  -- ignore any time 		M = nil 		S = nil 	else 		if H then 			-- It is not possible to set M or S without also setting H. 			date.hastime = true 		else 			H = 0 		end 		if not (0 <= H and H <= 23 and 				0 <= M and M <= 59 and 				0 <= S and S <= 59) then 			if date.want_fix then 				need_fix = true 			else 				return 			end 		end 	end 	date.want_fix = nil 	if need_fix then 		fix_numbers(numbers, y, m, d, H, M, S, date.partial, date.hastime, date.calendar) 		return set_date_from_numbers(date, numbers, options) 	end 	date.year = y    -- -9999 to 9999 ('n BC' → year = 1 - n) 	date.month = m   -- 1 to 12 (may be nil if partial) 	date.day = d     -- 1 to 31 (* = nil if partial) 	date.hour = H    -- 0 to 59 (*) 	date.minute = M  -- 0 to 59 (*) 	date.second = S  -- 0 to 59 (*) 	if type(options) == 'table' then 		for _, k in ipairs({ 'am', 'era', 'format' }) do 			if options[k] then 				date.options[k] = options[k] 			end 		end 	end 	return true end  local function make_option_table(options1, options2) 	-- If options1 is a string, return a table with its settings, or 	-- if it is a table, use its settings. 	-- Missing options are set from table options2 or defaults. 	-- If a default is used, a flag is set so caller knows the value was not intentionally set. 	-- Valid option settings are: 	-- am: 'am', 'a.m.', 'AM', 'A.M.' 	--     'pm', 'p.m.', 'PM', 'P.M.' (each has same meaning as corresponding item above) 	-- era: 'BCMINUS', 'BCNEGATIVE', 'BC', 'B.C.', 'BCE', 'B.C.E.', 'AD', 'A.D.', 'CE', 'C.E.' 	-- Option am = 'am' does not mean the hour is AM; it means 'am' or 'pm' is used, depending on the hour, 	--    and am = 'pm' has the same meaning. 	-- Similarly, era = 'BC' means 'BC' is used if year <= 0. 	-- BCMINUS displays a MINUS if year < 0 and the display format does not include %{era}. 	-- BCNEGATIVE is similar but displays a hyphen. 	local result = { bydefault = {} } 	if type(options1) == 'table' then 		result.am = options1.am 		result.era = options1.era 	elseif type(options1) == 'string' then 		-- Example: 'am:AM era:BC' or 'am=AM era=BC'. 		for item in options1:gmatch('%S+') do 			local lhs, rhs = item:match('^(%w+)[:=](.+)$') 			if lhs then 				result[lhs] = rhs 			end 		end 	end 	options2 = type(options2) == 'table' and options2 or {} 	local defaults = { am = 'am', era = 'BC' } 	for k, v in pairs(defaults) do 		if not result[k] then 			if options2[k] then 				result[k] = options2[k] 			else 				result[k] = v 				result.bydefault[k] = true 			end 		end 	end 	return result end  local ampm_options = { 	-- lhs = input text accepted as an am/pm option 	-- rhs = code used internally 	['am']   = 'am', 	['AM']   = 'AM', 	['a.m.'] = 'a.m.', 	['A.M.'] = 'A.M.', 	['pm']   = 'am',  -- same as am 	['PM']   = 'AM', 	['p.m.'] = 'a.m.', 	['P.M.'] = 'A.M.', }  local era_text = { 	-- Text for displaying an era with a positive year (after adjusting 	-- by replacing year with 1 - year if date.year <= 0). 	-- options.era = { year<=0 , year>0 } 	['BCMINUS']    = { 'BC'    ,     , isbc = true, sign = MINUS }, 	['BCNEGATIVE'] = { 'BC'    ,     , isbc = true, sign = '-'   }, 	['BC']         = { 'BC'    ,     , isbc = true }, 	['B.C.']       = { 'B.C.'  ,     , isbc = true }, 	['BCE']        = { 'BCE'   ,     , isbc = true }, 	['B.C.E.']     = { 'B.C.E.',     , isbc = true }, 	['AD']         = { 'BC'    , 'AD'   }, 	['A.D.']       = { 'B.C.'  , 'A.D.' }, 	['CE']         = { 'BCE'   , 'CE'   }, 	['C.E.']       = { 'B.C.E.', 'C.E.' }, }  local function get_era_for_year(era, year) 	return (era_text[era] or era_text['BC'])[year > 0 and 2 or 1] or end  local function strftime(date, format, options) 	-- Return date formatted as a string using codes similar to those 	-- in the C strftime library function. 	local sformat = string.format 	local shortcuts = { 		['%c'] = '%-I:%M %p %-d %B %-Y %{era}',  -- date and time: 2:30 pm 1 April 2016 		['%x'] = '%-d %B %-Y %{era}',            -- date:          1 April 2016 		['%X'] = '%-I:%M %p',                    -- time:          2:30 pm 	} 	if shortcuts[format] then 		format = shortcuts[format] 	end 	local codes = { 		a = { field = 'dayabbr' }, 		A = { field = 'dayname' }, 		b = { field = 'monthabbr' }, 		B = { field = 'monthname' }, 		u = { fmt = '%d'  , field = 'dowiso' }, 		w = { fmt = '%d'  , field = 'dow' }, 		d = { fmt = '%02d', fmt2 = '%d', field = 'day' }, 		m = { fmt = '%02d', fmt2 = '%d', field = 'month' }, 		Y = { fmt = '%04d', fmt2 = '%d', field = 'year' }, 		H = { fmt = '%02d', fmt2 = '%d', field = 'hour' }, 		M = { fmt = '%02d', fmt2 = '%d', field = 'minute' }, 		S = { fmt = '%02d', fmt2 = '%d', field = 'second' }, 		j = { fmt = '%03d', fmt2 = '%d', field = 'dayofyear' }, 		I = { fmt = '%02d', fmt2 = '%d', field = 'hour', special = 'hour12' }, 		p = { field = 'hour', special = 'am' }, 	} 	options = make_option_table(options, date.options) 	local amopt = options.am 	local eraopt = options.era 	local function replace_code(spaces, modifier, id) 		local code = codes[id] 		if code then 			local fmt = code.fmt 			if modifier == '-' and code.fmt2 then 				fmt = code.fmt2 			end 			local value = date[code.field] 			if not value then 				return nil  -- an undefined field in a partial date 			end 			local special = code.special 			if special then 				if special == 'hour12' then 					value = value % 12 					value = value == 0 and 12 or value 				elseif special == 'am' then 					local ap = ({ 						['a.m.'] = { 'a.m.', 'p.m.' }, 						['AM'] = { 'AM', 'PM' }, 						['A.M.'] = { 'A.M.', 'P.M.' }, 					})[ampm_options[amopt]] or { 'am', 'pm' } 					return (spaces ==  and  or ' ') .. (value < 12 and ap[1] or ap[2]) 				end 			end 			if code.field == 'year' then 				local sign = (era_text[eraopt] or {}).sign 				if not sign or format:find('%{era}', 1, true) then 					sign =  					if value <= 0 then 						value = 1 - value 					end 				else 					if value >= 0 then 						sign = 					else 						value = -value 					end 				end 				return spaces .. sign .. sformat(fmt, value) 			end 			return spaces .. (fmt and sformat(fmt, value) or value) 		end 	end 	local function replace_property(spaces, id) 		if id == 'era' then 			-- Special case so can use local era option. 			local result = get_era_for_year(eraopt, date.year) 			if result ==  then 				return 			end 			return (spaces ==  and  or ' ') .. result 		end 		local result = date[id] 		if type(result) == 'string' then 			return spaces .. result 		end 		if type(result) == 'number' then 			return  spaces .. tostring(result) 		end 		if type(result) == 'boolean' then 			return  spaces .. (result and '1' or '0') 		end 		-- This occurs if id is an undefined field in a partial date, or is the name of a function. 		return nil 	end 	local PERCENT = '\127PERCENT\127' 	return (format 		:gsub('%%%%', PERCENT) 		:gsub('(%s*)%%{(%w+)}', replace_property) 		:gsub('(%s*)%%(%-?)(%a)', replace_code) 		:gsub(PERCENT, '%%') 	) end  local function _date_text(date, fmt, options) 	-- Return a formatted string representing the given date. 	if not is_date(date) then 		error('date:text: need a date (use "date:text()" with a colon)', 2) 	end 	if type(fmt) == 'string' and fmt:match('%S') then 		if fmt:find('%', 1, true) then 			return strftime(date, fmt, options) 		end 	elseif date.partial then 		fmt = date.month and 'my' or 'y' 	else 		fmt = 'dmy' 		if date.hastime then 			fmt = (date.second > 0 and 'hms ' or 'hm ') .. fmt 		end 	end 	local function bad_format() 		-- For consistency with other format processing, return given format 		-- (or cleaned format if original was not a string) if invalid. 		return mw.text.nowiki(fmt) 	end 	if date.partial then 		-- Ignore days in standard formats like 'ymd'. 		if fmt == 'ym' or fmt == 'ymd' then 			fmt = date.month and '%Y-%m %{era}' or '%Y %{era}' 		elseif fmt == 'my' or fmt == 'dmy' or fmt == 'mdy' then 			fmt = date.month and '%B %-Y %{era}' or '%-Y %{era}' 		elseif fmt == 'y' then 			fmt = date.month and '%-Y %{era}' or '%-Y %{era}' 		else 			return bad_format() 		end 		return strftime(date, fmt, options) 	end 	local function hm_fmt() 		local plain = make_option_table(options, date.options).bydefault.am 		return plain and '%H:%M' or '%-I:%M %p' 	end 	local need_time = date.hastime 	local t = collection() 	for item in fmt:gmatch('%S+') do 		local f 		if item == 'hm' then 			f = hm_fmt() 			need_time = false 		elseif item == 'hms' then 			f = '%H:%M:%S' 			need_time = false 		elseif item == 'ymd' then 			f = '%Y-%m-%d %{era}' 		elseif item == 'mdy' then 			f = '%B %-d, %-Y %{era}' 		elseif item == 'dmy' then 			f = '%-d %B %-Y %{era}' 		else 			return bad_format() 		end 		t:add(f) 	end 	fmt = t:join(' ') 	if need_time then 		fmt = hm_fmt() .. ' ' .. fmt 	end 	return strftime(date, fmt, options) end  local day_info = { 	-- 0=Sun to 6=Sat 	[0] = { 'Sun', 'Sunday' }, 	{ 'Mon', 'Monday' }, 	{ 'Tue', 'Tuesday' }, 	{ 'Wed', 'Wednesday' }, 	{ 'Thu', 'Thursday' }, 	{ 'Fri', 'Friday' }, 	{ 'Sat', 'Saturday' }, }  local month_info = { 	-- 1=Jan to 12=Dec 	{ 'Jan', 'January' }, 	{ 'Feb', 'February' }, 	{ 'Mar', 'March' }, 	{ 'Apr', 'April' }, 	{ 'May', 'May' }, 	{ 'Jun', 'June' }, 	{ 'Jul', 'July' }, 	{ 'Aug', 'August' }, 	{ 'Sep', 'September' }, 	{ 'Oct', 'October' }, 	{ 'Nov', 'November' }, 	{ 'Dec', 'December' }, }  local function name_to_number(text, translate) 	if type(text) == 'string' then 		return translate[text:lower()] 	end end  local function day_number(text) 	return name_to_number(text, { 		sun = 0, sunday = 0, 		mon = 1, monday = 1, 		tue = 2, tuesday = 2, 		wed = 3, wednesday = 3, 		thu = 4, thursday = 4, 		fri = 5, friday = 5, 		sat = 6, saturday = 6, 	}) end  local function month_number(text) 	return name_to_number(text, { 		jan = 1, january = 1, 		feb = 2, february = 2, 		mar = 3, march = 3, 		apr = 4, april = 4, 		may = 5, 		jun = 6, june = 6, 		jul = 7, july = 7, 		aug = 8, august = 8, 		sep = 9, september = 9, sept = 9, 		oct = 10, october = 10, 		nov = 11, november = 11, 		dec = 12, december = 12, 	}) end  local function _list_text(list, fmt) 	-- Return a list of formatted strings from a list of dates. 	if not type(list) == 'table' then 		error('date:list:text: need "list:text()" with a colon', 2) 	end 	local result = { join = _list_join } 	for i, date in ipairs(list) do 		result[i] = date:text(fmt) 	end 	return result end  local function _date_list(date, spec) 	-- Return a possibly empty numbered table of dates meeting the specification. 	-- Dates in the list are in ascending order (oldest date first). 	-- The spec should be a string of form "<count> <day> <op>" 	-- where each item is optional and 	--   count = number of items wanted in list 	--   day = abbreviation or name such as Mon or Monday 	--   op = >, >=, <, <= (default is > meaning after date) 	-- If no count is given, the list is for the specified days in date's month. 	-- The default day is date's day. 	-- The spec can also be a positive or negative number: 	--   -5 is equivalent to '5 <' 	--   5  is equivalent to '5' which is '5 >' 	if not is_date(date) then 		error('date:list: need a date (use "date:list()" with a colon)', 2) 	end 	local list = { text = _list_text } 	if date.partial then 		return list 	end 	local count, offset, operation 	local ops = { 		['>='] = { before = false, include = true  }, 		['>']  = { before = false, include = false }, 		['<='] = { before = true , include = true  }, 		['<']  = { before = true , include = false }, 	} 	if spec then 		if type(spec) == 'number' then 			count = floor(spec + 0.5) 			if count < 0 then 				count = -count 				operation = ops['<'] 			end 		elseif type(spec) == 'string' then 			local num, day, op = spec:match('^%s*(%d*)%s*(%a*)%s*([<>=]*)%s*$') 			if not num then 				return list 			end 			if num ~=  then 				count = tonumber(num) 			end 			if day ~=  then 				local dow = day_number(day:gsub('[sS]$', ))  -- accept plural days 				if not dow then 					return list 				end 				offset = dow - date.dow 			end 			operation = ops[op] 		else 			return list 		end 	end 	offset = offset or 0 	operation = operation or ops['>'] 	local datefrom, dayfirst, daylast 	if operation.before then 		if offset > 0 or (offset == 0 and not operation.include) then 			offset = offset - 7 		end 		if count then 			if count > 1 then 				offset = offset - 7*(count - 1) 			end 			datefrom = date + offset 		else 			daylast = date.day + offset 			dayfirst = daylast % 7 			if dayfirst == 0 then 				dayfirst = 7 			end 		end 	else 		if offset < 0 or (offset == 0 and not operation.include) then 			offset = offset + 7 		end 		if count then 			datefrom = date + offset 		else 			dayfirst = date.day + offset 			daylast = date.monthdays 		end 	end 	if not count then 		if daylast < dayfirst then 			return list 		end 		count = floor((daylast - dayfirst)/7) + 1 		datefrom = Date(date, {day = dayfirst}) 	end 	for i = 1, count do 		if not datefrom then break end  -- exceeds date limits 		list[i] = datefrom 		datefrom = datefrom + 7 	end 	return list end  -- A table to get the current date/time (UTC), but only if needed. local current = setmetatable({}, { 	__index = function (self, key) 		local d = os.date('!*t') 		self.year = d.year 		self.month = d.month 		self.day = d.day 		self.hour = d.hour 		self.minute = d.min 		self.second = d.sec 		return rawget(self, key) 	end })  local function extract_date(newdate, text) 	-- Parse the date/time in text and return n, o where 	--   n = table of numbers with date/time fields 	--   o = table of options for AM/PM or AD/BC or format, if any 	-- or return nothing if date is known to be invalid. 	-- Caller determines if the values in n are valid. 	-- A year must be positive ('1' to '9999'); use 'BC' for BC. 	-- In a y-m-d string, the year must be four digits to avoid ambiguity 	-- ('0001' to '9999'). The only way to enter year <= 0 is by specifying 	-- the date as three numeric parameters like ymd Date(-1, 1, 1). 	-- Dates of form d/m/y, m/d/y, y/m/d are rejected as potentially ambiguous. 	local date, options = {}, {} 	if text:sub(-1) == 'Z' then 		-- Extract date/time from a Wikidata timestamp. 		-- The year can be 1 to 16 digits but this module handles 1 to 4 digits only. 		-- Examples: '+2016-06-21T14:30:00Z', '-0000000180-00-00T00:00:00Z'. 		local sign, y, m, d, H, M, S = text:match('^([+%-])(%d+)%-(%d%d)%-(%d%d)T(%d%d):(%d%d):(%d%d)Z$') 		if sign then 			y = tonumber(y) 			if sign == '-' and y > 0 then 				y = -y 			end 			if y <= 0 then 				options.era = 'BCE' 			end 			date.year = y 			m = tonumber(m) 			d = tonumber(d) 			H = tonumber(H) 			M = tonumber(M) 			S = tonumber(S) 			if m == 0 then 				newdate.partial = true 				return date, options 			end 			date.month = m 			if d == 0 then 				newdate.partial = true 				return date, options 			end 			date.day = d 			if H > 0 or M > 0 or S > 0 then 				date.hour = H 				date.minute = M 				date.second = S 			end 			return date, options 		end 		return 	end 	local function extract_ymd(item) 		-- Called when no day or month has been set. 		local y, m, d = item:match('^(%d%d%d%d)%-(%w+)%-(%d%d?)$') 		if y then 			if date.year then 				return 			end 			if m:match('^%d%d?$') then 				m = tonumber(m) 			else 				m = month_number(m) 			end 			if m then 				date.year = tonumber(y) 				date.month = m 				date.day = tonumber(d) 				return true 			end 		end 	end 	local function extract_day_or_year(item) 		-- Called when a day would be valid, or 		-- when a year would be valid if no year has been set and partial is set. 		local number, suffix = item:match('^(%d%d?%d?%d?)(.*)$') 		if number then 			local n = tonumber(number) 			if #number <= 2 and n <= 31 then 				suffix = suffix:lower() 				if suffix ==  or suffix == 'st' or suffix == 'nd' or suffix == 'rd' or suffix == 'th' then 					date.day = n 					return true 				end 			elseif suffix ==  and newdate.partial and not date.year then 				date.year = n 				return true 			end 		end 	end 	local function extract_month(item) 		-- A month must be given as a name or abbreviation; a number could be ambiguous. 		local m = month_number(item) 		if m then 			date.month = m 			return true 		end 	end 	local function extract_time(item) 		local h, m, s = item:match('^(%d%d?):(%d%d)(:?%d*)$') 		if date.hour or not h then 			return 		end 		if s ~= '' then 			s = s:match('^:(%d%d)$') 			if not s then 				return 			end 		end 		date.hour = tonumber(h) 		date.minute = tonumber(m) 		date.second = tonumber(s)  -- nil if empty string 		return true 	end 	local item_count = 0 	local index_time 	local function set_ampm(item) 		local H = date.hour 		if H and not options.am and index_time + 1 == item_count then 			options.am = ampm_options[item]  -- caller checked this is not nil 			if item:match('^[Aa]') then 				if not (1 <= H and H <= 12) then 					return 				end 				if H == 12 then 					date.hour = 0 				end 			else 				if not (1 <= H and H <= 23) then 					return 				end 				if H <= 11 then 					date.hour = H + 12 				end 			end 			return true 		end 	end 	for item in text:gsub(',', ' '):gsub(' ', ' '):gmatch('%S+') do 		item_count = item_count + 1 		if era_text[item] then 			-- Era is accepted in peculiar places. 			if options.era then 				return 			end 			options.era = item 		elseif ampm_options[item] then 			if not set_ampm(item) then 				return 			end 		elseif item:find(':', 1, true) then 			if not extract_time(item) then 				return 			end 			index_time = item_count 		elseif date.day and date.month then 			if date.year then 				return  -- should be nothing more so item is invalid 			end 			if not item:match('^(%d%d?%d?%d?)$') then 				return 			end 			date.year = tonumber(item) 		elseif date.day then 			if not extract_month(item) then 				return 			end 		elseif date.month then 			if not extract_day_or_year(item) then 				return 			end 		elseif extract_month(item) then 			options.format = 'mdy' 		elseif extract_ymd(item) then 			options.format = 'ymd' 		elseif extract_day_or_year(item) then 			if date.day then 				options.format = 'dmy' 			end 		else 			return 		end 	end 	if not date.year or date.year == 0 then 		return 	end 	local era = era_text[options.era] 	if era and era.isbc then 		date.year = 1 - date.year 	end 	return date, options end  local function autofill(date1, date2) 	-- Fill any missing month or day in each date using the 	-- corresponding component from the other date, if present, 	-- or with 1 if both dates are missing the month or day. 	-- This gives a good result for calculating the difference 	-- between two partial dates when no range is wanted. 	-- Return filled date1, date2 (two full dates). 	local function filled(a, b) 		-- Return date a filled, if necessary, with month and/or day from date b. 		-- The filled day is truncated to fit the number of days in the month. 		local fillmonth, fillday 		if not a.month then 			fillmonth = b.month or 1 		end 		if not a.day then 			fillday = b.day or 1 		end 		if fillmonth or fillday then  -- need to create a new date 			a = Date(a, { 				month = fillmonth, 				day = math.min(fillday or a.day, days_in_month(a.year, fillmonth or a.month, a.calendar)) 			}) 		end 		return a 	end 	return filled(date1, date2), filled(date2, date1) end  local function date_add_sub(lhs, rhs, is_sub) 	-- Return a new date from calculating (lhs + rhs) or (lhs - rhs), 	-- or return nothing if invalid. 	-- The result is nil if the calculated date exceeds allowable limits. 	-- Caller ensures that lhs is a date; its properties are copied for the new date. 	if lhs.partial then 		-- Adding to a partial is not supported. 		-- Can subtract a date or partial from a partial, but this is not called for that. 		return 	end 	local function is_prefix(text, word, minlen) 		local n = #text 		return (minlen or 1) <= n and n <= #word and text == word:sub(1, n) 	end 	local function do_days(n) 		local forcetime, jd 		if floor(n) == n then 			jd = lhs.jd 		else 			forcetime = not lhs.hastime 			jd = lhs.jdz 		end 		jd = jd + (is_sub and -n or n) 		if forcetime then 			jd = tostring(jd) 			if not jd:find('.', 1, true) then 				jd = jd .. '.0' 			end 		end 		return Date(lhs, 'juliandate', jd) 	end 	if type(rhs) == 'number' then 		-- Add/subtract days, including fractional days. 		return do_days(rhs) 	end 	if type(rhs) == 'string' then 		-- rhs is a single component like '26m' or '26 months' (with optional sign). 		-- Fractions like '3.25d' are accepted for the units which are handled as days. 		local sign, numstr, id = rhs:match('^%s*([+-]?)([%d%.]+)%s*(%a+)$') 		if sign then 			if sign == '-' then 				is_sub = not (is_sub and true or false) 			end 			local y, m, days 			local num = tonumber(numstr) 			if not num then 				return 			end 			id = id:lower() 			if is_prefix(id, 'years') then 				y = num 				m = 0 			elseif is_prefix(id, 'months') then 				y = floor(num / 12) 				m = num % 12 			elseif is_prefix(id, 'weeks') then 				days = num * 7 			elseif is_prefix(id, 'days') then 				days = num 			elseif is_prefix(id, 'hours') then 				days = num / 24 			elseif is_prefix(id, 'minutes', 3) then 				days = num / (24 * 60) 			elseif is_prefix(id, 'seconds') then 				days = num / (24 * 3600) 			else 				return 			end 			if days then 				return do_days(days) 			end 			if numstr:find('.', 1, true) then 				return 			end 			if is_sub then 				y = -y 				m = -m 			end 			assert(-11 <= m and m <= 11) 			y = lhs.year + y 			m = lhs.month + m 			if m > 12 then 				y = y + 1 				m = m - 12 			elseif m < 1 then 				y = y - 1 				m = m + 12 			end 			local d = math.min(lhs.day, days_in_month(y, m, lhs.calendar)) 			return Date(lhs, y, m, d) 		end 	end 	if is_diff(rhs) then 		local days = rhs.age_days 		if (is_sub or false) ~= (rhs.isnegative or false) then 			days = -days 		end 		return lhs + days 	end end  local full_date_only = { 	dayabbr = true, 	dayname = true, 	dow = true, 	dayofweek = true, 	dowiso = true, 	dayofweekiso = true, 	dayofyear = true, 	gsd = true, 	juliandate = true, 	jd = true, 	jdz = true, 	jdnoon = true, }  -- Metatable for a date's calculated fields. local datemt = { 	__index = function (self, key) 		if rawget(self, 'partial') then 			if full_date_only[key] then return end 			if key == 'monthabbr' or key == 'monthdays' or key == 'monthname' then 				if not self.month then return end 			end 		end 		local value 		if key == 'dayabbr' then 			value = day_info[self.dow][1] 		elseif key == 'dayname' then 			value = day_info[self.dow][2] 		elseif key == 'dow' then 			value = (self.jdnoon + 1) % 7  -- day-of-week 0=Sun to 6=Sat 		elseif key == 'dayofweek' then 			value = self.dow 		elseif key == 'dowiso' then 			value = (self.jdnoon % 7) + 1  -- ISO day-of-week 1=Mon to 7=Sun 		elseif key == 'dayofweekiso' then 			value = self.dowiso 		elseif key == 'dayofyear' then 			local first = Date(self.year, 1, 1, self.calendar).jdnoon 			value = self.jdnoon - first + 1  -- day-of-year 1 to 366 		elseif key == 'era' then 			-- Era text (never a negative sign) from year and options. 			value = get_era_for_year(self.options.era, self.year) 		elseif key == 'format' then 			value = self.options.format or 'dmy' 		elseif key == 'gsd' then 			-- GSD = 1 from 00:00:00 to 23:59:59 on 1 January 1 AD Gregorian calendar, 			-- which is from jd 1721425.5 to 1721426.49999. 			value = floor(self.jd - 1721424.5) 		elseif key == 'juliandate' or key == 'jd' or key == 'jdz' then 			local jd, jdz = julian_date(self) 			rawset(self, 'juliandate', jd) 			rawset(self, 'jd', jd) 			rawset(self, 'jdz', jdz) 			return key == 'jdz' and jdz or jd 		elseif key == 'jdnoon' then 			-- Julian date at noon (an integer) on the calendar day when jd occurs. 			value = floor(self.jd + 0.5) 		elseif key == 'isleapyear' then 			value = is_leap_year(self.year, self.calendar) 		elseif key == 'monthabbr' then 			value = month_info[self.month][1] 		elseif key == 'monthdays' then 			value = days_in_month(self.year, self.month, self.calendar) 		elseif key == 'monthname' then 			value = month_info[self.month][2] 		end 		if value ~= nil then 			rawset(self, key, value) 			return value 		end 	end, }  -- Date operators. local function mt_date_add(lhs, rhs) 	if not is_date(lhs) then 		lhs, rhs = rhs, lhs  -- put date on left (it must be a date for this to have been called) 	end 	return date_add_sub(lhs, rhs) end  local function mt_date_sub(lhs, rhs) 	if is_date(lhs) then 		if is_date(rhs) then 			return DateDiff(lhs, rhs) 		end 		return date_add_sub(lhs, rhs, true) 	end end  local function mt_date_concat(lhs, rhs) 	return tostring(lhs) .. tostring(rhs) end  local function mt_date_tostring(self) 	return self:text() end  local function mt_date_eq(lhs, rhs) 	-- Return true if dates identify same date/time where, for example, 	-- Date(-4712, 1, 1, 'Julian') == Date(-4713, 11, 24, 'Gregorian') is true. 	-- This is called only if lhs and rhs have the same type and the same metamethod. 	if lhs.partial or rhs.partial then 		-- One date is partial; the other is a partial or a full date. 		-- The months may both be nil, but must be the same. 		return lhs.year == rhs.year and lhs.month == rhs.month and lhs.calendar == rhs.calendar 	end 	return lhs.jdz == rhs.jdz end  local function mt_date_lt(lhs, rhs) 	-- Return true if lhs < rhs, for example, 	-- Date('1 Jan 2016') < Date('06:00 1 Jan 2016') is true. 	-- This is called only if lhs and rhs have the same type and the same metamethod. 	if lhs.partial or rhs.partial then 		-- One date is partial; the other is a partial or a full date. 		if lhs.calendar ~= rhs.calendar then 			return lhs.calendar == 'Julian' 		end 		if lhs.partial then 			lhs = lhs.partial.first 		end 		if rhs.partial then 			rhs = rhs.partial.first 		end 	end 	return lhs.jdz < rhs.jdz end  --[[ Examples of syntax to construct a date: Date(y, m, d, 'julian')             default calendar is 'gregorian' Date(y, m, d, H, M, S, 'julian') Date('juliandate', jd, 'julian')    if jd contains "." text output includes H:M:S Date('currentdate') Date('currentdatetime') Date('1 April 1995', 'julian')      parse date from text Date('1 April 1995 AD', 'julian')   using an era sets a flag to do the same for output Date('04:30:59 1 April 1995', 'julian') Date(date)                          copy of an existing date Date(date, t)                       same, updated with y,m,d,H,M,S fields from table t Date(t)                       		date with y,m,d,H,M,S fields from table t ]] function Date(...)  -- for forward declaration above 	-- Return a table holding a date assuming a uniform calendar always applies 	-- (proleptic Gregorian calendar or proleptic Julian calendar), or 	-- return nothing if date is invalid. 	-- A partial date has a valid year, however its month may be nil, and 	-- its day and time fields are nil. 	-- Field partial is set to false (if a full date) or a table (if a partial date). 	local calendars = { julian = 'Julian', gregorian = 'Gregorian' } 	local newdate = { 		_id = uniq, 		calendar = 'Gregorian',  -- default is Gregorian calendar 		hastime = false,  -- true if input sets a time 		hour = 0,  -- always set hour/minute/second so don't have to handle nil 		minute = 0, 		second = 0, 		options = {}, 		list = _date_list, 		subtract = function (self, rhs, options) 			return DateDiff(self, rhs, options) 		end, 		text = _date_text, 	} 	local argtype, datetext, is_copy, jd_number, tnums 	local numindex = 0 	local numfields = { 'year', 'month', 'day', 'hour', 'minute', 'second' } 	local numbers = {} 	for _, v in ipairs({...}) do 		v = strip_to_nil(v) 		local vlower = type(v) == 'string' and v:lower() or nil 		if v == nil then 			-- Ignore empty arguments after stripping so modules can directly pass template parameters. 		elseif calendars[vlower] then 			newdate.calendar = calendars[vlower] 		elseif vlower == 'partial' then 			newdate.partial = true 		elseif vlower == 'fix' then 			newdate.want_fix = true 		elseif is_date(v) then 			-- Copy existing date (items can be overridden by other arguments). 			if is_copy or tnums then 				return 			end 			is_copy = true 			newdate.calendar = v.calendar 			newdate.partial = v.partial 			newdate.hastime = v.hastime 			newdate.options = v.options 			newdate.year = v.year 			newdate.month = v.month 			newdate.day = v.day 			newdate.hour = v.hour 			newdate.minute = v.minute 			newdate.second = v.second 		elseif type(v) == 'table' then 			if tnums then 				return 			end 			tnums = {} 			local tfields = { year=1, month=1, day=1, hour=2, minute=2, second=2 } 			for tk, tv in pairs(v) do 				if tfields[tk] then 					tnums[tk] = tonumber(tv) 				end 				if tfields[tk] == 2 then 					newdate.hastime = true 				end 			end 		else 			local num = tonumber(v) 			if not num and argtype == 'setdate' and numindex == 1 then 				num = month_number(v) 			end 			if num then 				if not argtype then 					argtype = 'setdate' 				end 				if argtype == 'setdate' and numindex < 6 then 					numindex = numindex + 1 					numbers[numfields[numindex]] = num 				elseif argtype == 'juliandate' and not jd_number then 					jd_number = num 					if type(v) == 'string' then 						if v:find('.', 1, true) then 							newdate.hastime = true 						end 					elseif num ~= floor(num) then 						-- The given value was a number. The time will be used 						-- if the fractional part is nonzero. 						newdate.hastime = true 					end 				else 					return 				end 			elseif argtype then 				return 			elseif type(v) == 'string' then 				if v == 'currentdate' or v == 'currentdatetime' or v == 'juliandate' then 					argtype = v 				else 					argtype = 'datetext' 					datetext = v 				end 			else 				return 			end 		end 	end 	if argtype == 'datetext' then 		if tnums or not set_date_from_numbers(newdate, extract_date(newdate, datetext)) then 			return 		end 	elseif argtype == 'juliandate' then 		newdate.partial = nil 		newdate.jd = jd_number 		if not set_date_from_jd(newdate) then 			return 		end 	elseif argtype == 'currentdate' or argtype == 'currentdatetime' then 		newdate.partial = nil 		newdate.year = current.year 		newdate.month = current.month 		newdate.day = current.day 		if argtype == 'currentdatetime' then 			newdate.hour = current.hour 			newdate.minute = current.minute 			newdate.second = current.second 			newdate.hastime = true 		end 		newdate.calendar = 'Gregorian'  -- ignore any given calendar name 	elseif argtype == 'setdate' then 		if tnums or not set_date_from_numbers(newdate, numbers) then 			return 		end 	elseif not (is_copy or tnums) then 		return 	end 	if tnums then 		newdate.jd = nil  -- force recalculation in case jd was set before changes from tnums 		if not set_date_from_numbers(newdate, tnums) then 			return 		end 	end 	if newdate.partial then 		local year = newdate.year 		local month = newdate.month 		local first = Date(year, month or 1, 1, newdate.calendar) 		month = month or 12 		local last = Date(year, month, days_in_month(year, month), newdate.calendar) 		newdate.partial = { first = first, last = last } 	else 		newdate.partial = false  -- avoid index lookup 	end 	setmetatable(newdate, datemt) 	local readonly = {} 	local mt = { 		__index = newdate, 		__newindex = function(t, k, v) error('date.' .. tostring(k) .. ' is read-only', 2) end, 		__add = mt_date_add, 		__sub = mt_date_sub, 		__concat = mt_date_concat, 		__tostring = mt_date_tostring, 		__eq = mt_date_eq, 		__lt = mt_date_lt, 	} 	return setmetatable(readonly, mt) end  local function _diff_age(diff, code, options) 	-- Return a tuple of integer values from diff as specified by code, except that 	-- each integer may be a list of two integers for a diff with a partial date, or 	-- return nil if the code is not supported. 	-- If want round, the least significant unit is rounded to nearest whole unit. 	-- For a duration, an extra day is added. 	local wantround, wantduration, wantrange 	if type(options) == 'table' then 		wantround = options.round 		wantduration = options.duration 		wantrange = options.range 	else 		wantround = options 	end 	if not is_diff(diff) then 		local f = wantduration and 'duration' or 'age' 		error(f .. ': need a date difference (use "diff:' .. f .. '()" with a colon)', 2) 	end 	if diff.partial then 		-- Ignore wantround, wantduration. 		local function choose(v) 			if type(v) == 'table' then 				if not wantrange or v[1] == v[2] then 					-- Example: Date('partial', 2005) - Date('partial', 2001) gives 					-- diff.years = { 3, 4 } to show the range of possible results. 					-- If do not want a range, choose the second value as more expected. 					return v[2] 				end 			end 			return v 		end 		if code == 'ym' or code == 'ymd' then 			if not wantrange and diff.iszero then 				-- This avoids an unexpected result such as 				-- Date('partial', 2001) - Date('partial', 2001) 				-- giving diff = { years = 0, months = { 0, 11 } } 				-- which would be reported as 0 years and 11 months. 				return 0, 0 			end 			return choose(diff.partial.years), choose(diff.partial.months) 		end 		if code == 'y' then 			return choose(diff.partial.years) 		end 		if code == 'm' or code == 'w' or code == 'd' then 			return choose({ diff.partial.mindiff:age(code), diff.partial.maxdiff:age(code) }) 		end 		return nil 	end 	local extra_days = wantduration and 1 or 0 	if code == 'wd' or code == 'w' or code == 'd' then 		local offset = wantround and 0.5 or 0 		local days = diff.age_days + extra_days 		if code == 'wd' or code == 'd' then 			days = floor(days + offset) 			if code == 'd' then 				return days 			end 			return floor(days/7), days % 7 		end 		return floor(days/7 + offset) 	end 	local H, M, S = diff.hours, diff.minutes, diff.seconds 	if code == 'dh' or code == 'dhm' or code == 'dhms' or code == 'h' or code == 'hm' or code == 'hms' or code == 'M' or code == 's' then 		local days = floor(diff.age_days + extra_days) 		local inc_hour 		if wantround then 			if code == 'dh' or code == 'h' then 				if M >= 30 then 					inc_hour = true 				end 			elseif code == 'dhm' or code == 'hm' then 				if S >= 30 then 					M = M + 1 					if M >= 60 then 						M = 0 						inc_hour = true 					end 				end 			elseif code == 'M' then 				if S >= 30 then 					M = M + 1 				end 			else 				-- Nothing needed because S is an integer. 			end 			if inc_hour then 				H = H + 1 				if H >= 24 then 					H = 0 					days = days + 1 				end 			end 		end 		if code == 'dh' or code == 'dhm' or code == 'dhms' then 			if code == 'dh' then 				return days, H 			elseif code == 'dhm' then 				return days, H, M 			else 				return days, H, M, S 			end 		end 		local hours = days * 24 + H 		if code == 'h' then 			return hours 		elseif code == 'hm' then 			return hours, M 		elseif code == 'M' or code == 's' then 			M = hours * 60 + M 			if code == 'M' then 				return M 			end 			return M * 60 + S 		end 		return hours, M, S 	end 	if wantround then 		local inc_hour 		if code == 'ymdh' or code == 'ymwdh' then 			if M >= 30 then 				inc_hour = true 			end 		elseif code == 'ymdhm' or code == 'ymwdhm' then 			if S >= 30 then 				M = M + 1 				if M >= 60 then 					M = 0 					inc_hour = true 				end 			end 		elseif code == 'ymd' or code == 'ymwd' or code == 'yd' or code == 'md' then 			if H >= 12 then 				extra_days = extra_days + 1 			end 		end 		if inc_hour then 			H = H + 1 			if H >= 24 then 				H = 0 				extra_days = extra_days + 1 			end 		end 	end 	local y, m, d = diff.years, diff.months, diff.days 	if extra_days > 0 then 		d = d + extra_days 		if d > 28 or code == 'yd' then 			-- Recalculate in case have passed a month. 			diff = diff.date1 + extra_days - diff.date2 			y, m, d = diff.years, diff.months, diff.days 		end 	end 	if code == 'ymd' then 		return y, m, d 	elseif code == 'yd' then 		if y > 0 then 			-- It is known that diff.date1 > diff.date2. 			diff = diff.date1 - (diff.date2 + (y .. 'y')) 		end 		return y, floor(diff.age_days) 	elseif code == 'md' then 		return y * 12 + m, d 	elseif code == 'ym' or code == 'm' then 		if wantround then 			if d >= 16 then 				m = m + 1 				if m >= 12 then 					m = 0 					y = y + 1 				end 			end 		end 		if code == 'ym' then 			return y, m 		end 		return y * 12 + m 	elseif code == 'ymw' then 		local weeks = floor(d/7) 		if wantround then 			local days = d % 7 			if days > 3 or (days == 3 and H >= 12) then 				weeks = weeks + 1 			end 		end 		return y, m, weeks 	elseif code == 'ymwd' then 		return y, m, floor(d/7), d % 7 	elseif code == 'ymdh' then 		return y, m, d, H 	elseif code == 'ymwdh' then 		return y, m, floor(d/7), d % 7, H 	elseif code == 'ymdhm' then 		return y, m, d, H, M 	elseif code == 'ymwdhm' then 		return y, m, floor(d/7), d % 7, H, M 	end 	if code == 'y' then 		if wantround and m >= 6 then 			y = y + 1 		end 		return y 	end 	return nil end  local function _diff_duration(diff, code, options) 	if type(options) ~= 'table' then 		options = { round = options } 	end 	options.duration = true 	return _diff_age(diff, code, options) end  -- Metatable for some operations on date differences. diffmt = {  -- for forward declaration above 	__concat = function (lhs, rhs) 		return tostring(lhs) .. tostring(rhs) 	end, 	__tostring = function (self) 		return tostring(self.age_days) 	end, 	__index = function (self, key) 		local value 		if key == 'age_days' then 			if rawget(self, 'partial') then 				local function jdz(date) 					return (date.partial and date.partial.first or date).jdz 				end 				value = jdz(self.date1) - jdz(self.date2) 			else 				value = self.date1.jdz - self.date2.jdz 			end 		end 		if value ~= nil then 			rawset(self, key, value) 			return value 		end 	end, }  function DateDiff(date1, date2, options)  -- for forward declaration above 	-- Return a table with the difference between two dates (date1 - date2). 	-- The difference is negative if date1 is older than date2. 	-- Return nothing if invalid. 	-- If d = date1 - date2 then 	--     date1 = date2 + d 	-- If date1 >= date2 and the dates have no H:M:S time specified then 	--     date1 = date2 + (d.years..'y') + (d.months..'m') + d.days 	-- where the larger time units are added first. 	-- The result of Date(2015,1,x) + '1m' is Date(2015,2,28) for 	-- x = 28, 29, 30, 31. That means, for example, 	--     d = Date(2015,3,3) - Date(2015,1,31) 	-- gives d.years, d.months, d.days = 0, 1, 3 (excluding date1). 	if not (is_date(date1) and is_date(date2) and date1.calendar == date2.calendar) then 		return 	end 	local wantfill 	if type(options) == 'table' then 		wantfill = options.fill 	end 	local isnegative = false 	local iszero = false 	if date1 < date2 then 		isnegative = true 		date1, date2 = date2, date1 	elseif date1 == date2 then 		iszero = true 	end 	-- It is known that date1 >= date2 (period is from date2 to date1). 	if date1.partial or date2.partial then 		-- Two partial dates might have timelines: 		---------------------A=================B--- date1 is from A to B inclusive 		--------C=======D-------------------------- date2 is from C to D inclusive 		-- date1 > date2 iff A > C (date1.partial.first > date2.partial.first) 		-- The periods can overlap ('April 2001' - '2001'): 		-------------A===B------------------------- A=2001-04-01  B=2001-04-30 		--------C=====================D------------ C=2001-01-01  D=2001-12-31 		if wantfill then 			date1, date2 = autofill(date1, date2) 		else 			local function zdiff(date1, date2) 				local diff = date1 - date2 				if diff.isnegative then 					return date1 - date1  -- a valid diff in case we call its methods 				end 				return diff 			end 			local function getdate(date, which) 				return date.partial and date.partial[which] or date 			end 			local maxdiff = zdiff(getdate(date1, 'last'), getdate(date2, 'first')) 			local mindiff = zdiff(getdate(date1, 'first'), getdate(date2, 'last')) 			local years, months 			if maxdiff.years == mindiff.years then 				years = maxdiff.years 				if maxdiff.months == mindiff.months then 					months = maxdiff.months 				else 					months = { mindiff.months, maxdiff.months } 				end 			else 				years = { mindiff.years, maxdiff.years } 			end 			return setmetatable({ 				date1 = date1, 				date2 = date2, 				partial = { 					years = years, 					months = months, 					maxdiff = maxdiff, 					mindiff = mindiff, 				}, 				isnegative = isnegative, 				iszero = iszero, 				age = _diff_age, 				duration = _diff_duration, 			}, diffmt) 		end 	end 	local y1, m1 = date1.year, date1.month 	local y2, m2 = date2.year, date2.month 	local years = y1 - y2 	local months = m1 - m2 	local d1 = date1.day + hms(date1) 	local d2 = date2.day + hms(date2) 	local days, time 	if d1 >= d2 then 		days = d1 - d2 	else 		months = months - 1 		-- Get days in previous month (before the "to" date) given December has 31 days. 		local dpm = m1 > 1 and days_in_month(y1, m1 - 1, date1.calendar) or 31 		if d2 >= dpm then 			days = d1 - hms(date2) 		else 			days = dpm - d2 + d1 		end 	end 	if months < 0 then 		years = years - 1 		months = months + 12 	end 	days, time = math.modf(days) 	local H, M, S = h_m_s(time) 	return setmetatable({ 		date1 = date1, 		date2 = date2, 		partial = false,  -- avoid index lookup 		years = years, 		months = months, 		days = days, 		hours = H, 		minutes = M, 		seconds = S, 		isnegative = isnegative, 		iszero = iszero, 		age = _diff_age, 		duration = _diff_duration, 	}, diffmt) end  return { 	_current = current, 	_Date = Date, 	_days_in_month = days_in_month, }