Module:Date

-- Date functions for implementing templates and for use by other modules. -- I18N and time zones are not supported.

local MINUS = '−' -- Unicode U+2212 MINUS SIGN

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 = function (self, sep) return table.concat(self, sep) end, } end

local function strip_to_nil(text) -- If text is a string, return its trimmed content, or nil. -- Otherwise return text (convenient when Date fields are provided from	-- another module which is able to pass, for example, a number). if type(text) == 'string' then text = text:match('(%S.-)%s*$') end return text end

local function number_name(number, singular, plural, sep) -- Return the given number, converted to a string, with the -- separator (default space) and singular or plural name appended. plural = plural or (singular .. 's') sep = sep or ' ' return tostring(number) .. sep .. ((number == 1) and singular or plural) 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). local month_days = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } if month == 2 and is_leap_year(year, calname) then return 29 end return month_days[month] 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 floor = math.floor local offset local a = floor((14 - date.month)/12) local y = date.year + 4800 - a	if date.calname == '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 + (date.hour + (date.minute + date.second / 60) /60) / 24 - 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 floor = math.floor local calname = date.calname local jd = date.jd	local limits -- min/max limits for date ranges −9999-01-01 to 9999-12-31 if calname == 'Julian' then limits = { -1931076.5, 5373557.49999 } elseif calname == 'Gregorian' then limits = { -1930999.5, 5373484.49999 } else limits = { 1, 0 } -- impossible end if not (limits[1] <= jd and jd <= limits[2]) then return end local jdn = floor(jd) if date.hastime then local time = jd - jdn local hour if time >= 0.5 then jdn = jdn + 1 time = time - 0.5 hour = 0 else hour = 12 end time = floor(time * 24 * 3600 + 0.5) -- number of seconds after hour date.second = time % 60 time = floor(time / 60) date.minute = time % 60 date.hour = hour + floor(time / 60) 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 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.y or numbers[1] local m = numbers.m or numbers[2] local d = numbers.d or numbers[3] local H = numbers.H or numbers[4] local M = numbers.M or numbers[5] or 0 local S = numbers.S or numbers[6] or 0 if not (y and m and d) then return end if not (-9999 <= y and y <= 9999 and 1 <= m and m <= 12 and				1 <= d and d <= days_in_month(y, m, date.calname)) then return end if H then 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 return end date.year = y   -- -9999 to 9999 ('n BC' → year = 1 - n)	date.month = m   -- 1 to 12 date.day = d    -- 1 to 31 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' }) 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 options2 or defaults. -- Valid option settings are: -- am: 'am', 'a.m.', 'AM', 'A.M.' -- 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. -- 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 = {} if type(options1) == 'table' then result = options1 elseif type(options1) == 'string' then -- Example: '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		result[k] = result[k] or options2[k] or v	end return result end

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 'BC'] or {})[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 = 'doy' }, 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] 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.' },					})[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, for example, if id 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 formatted string from given date. if type(fmt) ~= 'string' then fmt = '%-d %B %-Y %{era}' if date.hastime then if date.second > 0 then fmt = '%H:%M:%S ' .. fmt else fmt = '%H:%M ' .. fmt end end return strftime(date, fmt, options) end if fmt:find('%', 1, true) then return strftime(date, fmt, options) end local t = collection for item in fmt:gmatch('%S+') do		local f		if item == 'hm' then f = '%H:%M' elseif item == 'hms' then f = '%H:%M:%S' 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 '(invalid format)' end t:add(f) end return strftime(date, t:join(' '), 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 month_number(text) if type(text) == 'string' then local month_names = { 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, oct = 10, october = 10, nov = 11, november = 11, dec = 12, december = 12 }		return month_names[text:lower] end end

-- A table to get the current year/month/day (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(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, 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 ambiguous. local date, options = {}, {} local function extract_ymd(item) local ystr, mstr, dstr = item:match('^(%d%d%d%d)-(%w+)-(%d%d?)$') if ystr then local m			if mstr:match('^%d%d?$') then m = tonumber(mstr) else m = month_number(mstr) end if m then date.y = tonumber(ystr) date.m = m				date.d = tonumber(dstr) return true end end end local function extract_month(item) -- A month must be given as a name or abbreviation; a number would be ambiguous. local m = month_number(item) if m then date.m = m			return true end end local function extract_time(item) local h, m, s = item:match('^(%d%d?):(%d%d)(:?%d*)$') if date.H or not h then return end if s ~= '' then s = s:match('^:(%d%d)$') if not s then return end end date.H = tonumber(h) date.M = tonumber(m) date.S = tonumber(s) -- nil if empty string return true end local ampm_options = { ['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 item_count = 0 local index_time local function set_ampm(item) local H = date.H		if H and not options.am and index_time + 1 == item_count then options.am = ampm_options[item] if item:match('^[Aa]') then if not (1 <= H and H <= 12) then return end if H == 12 then date.H = 0 end else if not (1 <= H and H <= 23) then return end if H <= 11 then date.H = H + 12 end end return true end end for item in text: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.d and date.m then if date.y then return -- should be nothing more so item is invalid end if not item:match('^(%d%d?%d?%d?)$') then return end date.y = tonumber(item) elseif date.d then if not extract_month(item) then return end elseif date.m then if not item:match('^(%d%d?)$') then return end date.d = tonumber(item) elseif not extract_ymd(item) then if item:match('^(%d%d?)$') then date.d = tonumber(item) elseif not extract_month(item) then return end end end if not date.y or date.y == 0 then return end local era = era_text[options.era] if era and era.isbc then date.y = 1 - date.y	end return date, options end

local Date, DateDiff, datemt -- forward declarations

local function is_date(t) return type(t) == 'table' and getmetatable(t) == datemt 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. -- Caller ensures that lhs is a date; its properties are copied for the new date. 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) if is_sub then n = -n end return Date(lhs, 'juliandate', lhs.jd + n)	end if type(rhs) == 'number' then -- Add days, including fractional days. return do_days(rhs) end if type(rhs) == 'string' then -- rhs is a single component like '26m' or '26 months' (unsigned integer only). local num, id = rhs:match('^%s*(%d+)%s*(%a+)$') if num then local y, m			num = tonumber(num) id = id:lower if is_prefix(id, 'years') then y = num m = 0 elseif is_prefix(id, 'months') then y = math.floor(num / 12) m = num % 12 elseif is_prefix(id, 'weeks') then return do_days(num * 7) elseif is_prefix(id, 'days') then return do_days(num) elseif is_prefix(id, 'hours') then return do_days(num / 24) elseif is_prefix(id, 'minutes', 3) then return do_days(num / (24 * 60)) elseif is_prefix(id, 'seconds') then return do_days(num / (24 * 3600)) else 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.calname)) return Date(lhs, y, m, d)		end end end

-- Metatable for some operations on dates. datemt = { -- for forward declaration above __add = function (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, __sub = function (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, __concat = function (lhs, rhs) return tostring(lhs) .. tostring(rhs) end, __tostring = function (self) return self:text end, __eq = function (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 only called if lhs and rhs have the same metatable. return lhs.jdz == rhs.jdz end, __lt = function (lhs, rhs) -- Return true if lhs < rhs, for example, -- Date('1 Jan 2016') < Date('06:00 1 Jan 2016') is true. -- This is only called if lhs and rhs have the same metatable. return lhs.jdz < rhs.jdz end, __index = function (self, key) 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.jd + 1) % 7 -- day-of-week 0=Sun to 6=Sat elseif key == 'dowiso' then value = (self.jd % 7) + 1 -- ISO day-of-week 1=Mon to 7=Sun elseif key == 'doy' then local first = Date(self.year, 1, 1, self.calname).jd			value = self.jd - first + 1 -- day-of-year 1 to 366 elseif key == 'era' then -- Era text (not a negative sign) from year and options. value = get_era_for_year(self.options.era, self.year) elseif key == 'gsd' then -- GSD = 1 from 00:00:00 to 23:59:59 on 1 January 1 AD Gregorian calendar, -- which is JDN = 1721426, and is from jd 1721425.5 to 1721426.49999. value = math.floor(self.jd - 1721424.5) elseif key == 'jd' or key == 'jdz' then local jd, jdz = julian_date(self) rawset(self, 'jd', jd) rawset(self, 'jdz', jdz) return key == 'jd' and jd or jdz elseif key == 'is_leap_year' then value = is_leap_year(self.year, self.calname) elseif key == 'monthabbr' then value = month_info[self.month][1] elseif key == 'monthname' then value = month_info[self.month][2] end if value ~= nil then rawset(self, key, value) return value end end, }

local function _month_days(date, month) return days_in_month(date.year, month, date.calname) 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 LATER: Following is not yet implemented: Date('currentdate', H, M, S)        current date with given time 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. local is_copy local calendars = { julian = 'Julian', gregorian = 'Gregorian' } local result = { calname = '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, month_days = _month_days, options = make_option_table, text = _date_text, }	local argtype, datetext local numbers = collection 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 result.calname = calendars[vlower] elseif is_date(v) then -- Copy existing date (items can be overridden by other arguments). if is_copy then return end is_copy = true result.calname = v.calname result.hastime = v.hastime result.options = v.options result.year = v.year result.month = v.month result.day = v.day result.hour = v.hour result.minute = v.minute result.second = v.second else local num = tonumber(v) if not num and argtype == 'setdate' and numbers.n == 1 then num = month_number(v) end if num then if not argtype then argtype = 'setdate' end numbers:add(num) if argtype == 'juliandate' then if type(v) == 'string' then if v:find('.', 1, true) then result.hastime = true end elseif num ~= math.floor(num) then -- The given value was a number. The time will be used -- if the fractional part is nonzero. result.hastime = true end 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 not (numbers.n == 0 and				set_date_from_numbers(result, extract_date(datetext))) then return end elseif argtype == 'juliandate' then result.jd = numbers[1] if not (numbers.n == 1 and set_date_from_jd(result)) then return end elseif argtype == 'currentdate' or argtype == 'currentdatetime' then result.year = current.year result.month = current.month result.day = current.day if argtype == 'currentdatetime' then result.hour = current.hour result.minute = current.minute result.second = current.second result.hastime = true end result.calname = 'Gregorian' -- ignore any given calendar name elseif argtype == 'setdate' then if not set_date_from_numbers(result, numbers) then return end elseif not is_copy then return end return setmetatable(result, datemt) end

function DateDiff(date1, date2) -- for forward declaration above -- Return a table with the difference between the two dates (date1 - date2). -- The difference is negative if date2 is more recent than date1. -- Return nothing if invalid. if not (date1 and date2 and date1.calname == date2.calname) then return end local isnegative if date1 < date2 then isnegative = true date1, date2 = date2, date1 end -- It is known that date1 >= date2. local y1, m1 = date1.year, date1.month local y2, m2 = date2.year, date2.month local years, months, days = y1 - y2, m1 - m2, date1.day - date2.day if days < 0 then days = days + days_in_month(y2, m2, date2.calname) months = months - 1 end if months < 0 then months = months + 12 years = years - 1 end return { years = years, months = months, days = days, isnegative = isnegative, age_ym = function (self) -- Return text specifying difference in years, months. local sign = self.isnegative and MINUS or '' local mtext = number_name(self.months, 'month') local result if self.years > 0 then local ytext = number_name(self.years, 'year') if self.months == 0 then result = ytext else result = ytext .. ', ' .. mtext end else if self.months == 0 then sign = '' end result = mtext end return sign .. result end, } end

return { _current = current, _Date = Date, _DateDiff = DateDiff, _days_in_month = days_in_month, }