Difference between revisions of "Module:Date"
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imported>Johnuniq (tweak formatted output; extract_date to parse an input date string) |
imported>Johnuniq (major refactor, mostly working now; add/subtract with a date; remove template handling which will be in Module:Age) |
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Line 19: | Line 19: | ||
local function strip_to_nil(text) | local function strip_to_nil(text) | ||
− | + | -- If text is a string, return its trimmed content, or nil. | |
− | -- If text is a | + | -- Otherwise return text (convenient when Date fields are provided from |
− | -- Otherwise return text (convenient when | + | -- another module which is able to pass, for example, a number). |
if type(text) == 'string' then | if type(text) == 'string' then | ||
− | + | text = text:match('(%S.-)%s*$') | |
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
end | end | ||
return text | return text | ||
Line 63: | Line 56: | ||
-- Return jd, jdz from a Julian or Gregorian calendar date where | -- Return jd, jdz from a Julian or Gregorian calendar date where | ||
-- jd = Julian date and its fractional part is zero at noon | -- jd = Julian date and its fractional part is zero at noon | ||
− | -- jdz = | + | -- jdz = same, but assume time is 00:00:00 if no time given |
-- http://www.tondering.dk/claus/cal/julperiod.php#formula | -- http://www.tondering.dk/claus/cal/julperiod.php#formula | ||
-- Testing shows this works for all dates from year -9999 to 9999! | -- Testing shows this works for all dates from year -9999 to 9999! | ||
Line 69: | Line 62: | ||
-- 1 January 4713 BC = (-4712, 1, 1) Julian calendar | -- 1 January 4713 BC = (-4712, 1, 1) Julian calendar | ||
-- 24 November 4714 BC = (-4713, 11, 24) Gregorian calendar | -- 24 November 4714 BC = (-4713, 11, 24) Gregorian calendar | ||
− | |||
− | |||
− | |||
local floor = math.floor | local floor = math.floor | ||
local offset | local offset | ||
Line 82: | Line 72: | ||
end | end | ||
local m = date.month + 12*a - 3 | local m = date.month + 12*a - 3 | ||
− | local | + | local jd = date.day + floor((153*m + 2)/5) + 365*y + offset |
− | |||
if date.hastime then | if date.hastime then | ||
− | + | jd = jd + (date.hour + (date.minute + date.second / 60) /60) / 24 - 0.5 | |
− | + | return jd, jd | |
− | |||
− | |||
− | |||
end | end | ||
− | + | return jd, jd - 0.5 | |
− | return jd, jd | ||
end | end | ||
local function set_date_from_jd(date) | local function set_date_from_jd(date) | ||
-- Set the fields of table date from its Julian date field. | -- 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 | -- http://www.tondering.dk/claus/cal/julperiod.php#formula | ||
-- This handles the proleptic Julian and Gregorian calendars. | -- This handles the proleptic Julian and Gregorian calendars. | ||
Line 112: | Line 98: | ||
end | end | ||
if not (limits[1] <= jd and jd <= limits[2]) then | if not (limits[1] <= jd and jd <= limits[2]) then | ||
− | |||
return | return | ||
end | end | ||
− | |||
local jdn = floor(jd) | local jdn = floor(jd) | ||
if date.hastime then | if date.hastime then | ||
Line 152: | Line 136: | ||
date.month = m + 3 - 12*floor(m/10) | date.month = m + 3 - 12*floor(m/10) | ||
date.year = 100*b + d - 4800 + floor(m/10) | date.year = 100*b + d - 4800 + floor(m/10) | ||
+ | return true | ||
end | end | ||
Line 189: | Line 174: | ||
date.minute = M -- 0 to 59 | date.minute = M -- 0 to 59 | ||
date.second = S -- 0 to 59 | date.second = S -- 0 to 59 | ||
− | |||
if type(options) == 'table' then | if type(options) == 'table' then | ||
for _, k in ipairs({ 'am', 'era' }) do | for _, k in ipairs({ 'am', 'era' }) do | ||
Line 200: | Line 184: | ||
end | end | ||
− | local function make_option_table( | + | local function make_option_table(options1, options2) |
− | -- If | + | -- If options1 is a string, return a table with its settings, or |
− | -- | + | -- if it is a table, use its settings. |
− | if type( | + | -- 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' | -- Example: 'am:AM era:BC' | ||
− | + | for item in options1:gmatch('%S+') do | |
− | for item in | + | local lhs, rhs = item:match('^(%w+):(.+)$') |
− | local lhs, rhs = item:match('^(%w+):(. | ||
if lhs then | if lhs then | ||
result[lhs] = rhs | result[lhs] = rhs | ||
end | end | ||
end | end | ||
− | |||
end | end | ||
− | return options | + | 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 | end | ||
Line 220: | Line 238: | ||
-- Return date formatted as a string using codes similar to those | -- Return date formatted as a string using codes similar to those | ||
-- in the C strftime library function. | -- in the C strftime library function. | ||
− | + | local sformat = string.format | |
− | |||
− | |||
local shortcuts = { | local shortcuts = { | ||
− | ['%c'] = '%-I:%M %p %-d %B %Y%{era}', -- date and time: 2:30 pm 1 April 2016 | + | ['%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'] = '%-d %B %-Y %{era}', -- date: 1 April 2016 |
− | ['%X'] = '%-I:%M %p', | + | ['%X'] = '%-I:%M %p', -- time: 2:30 pm |
} | } | ||
+ | if shortcuts[format] then | ||
+ | format = shortcuts[format] | ||
+ | end | ||
local codes = { | local codes = { | ||
a = { field = 'dayabbr' }, | a = { field = 'dayabbr' }, | ||
Line 245: | Line 264: | ||
p = { field = 'hour', special = 'am' }, | p = { field = 'hour', special = 'am' }, | ||
} | } | ||
− | options = make_option_table(options | + | options = make_option_table(options, date.options) |
local amopt = options.am | local amopt = options.am | ||
local eraopt = options.era | local eraopt = options.era | ||
− | local function replace_code(modifier, id) | + | local function replace_code(spaces, modifier, id) |
local code = codes[id] | local code = codes[id] | ||
if code then | if code then | ||
Line 267: | Line 286: | ||
['A.M.'] = { 'A.M.', 'P.M.' }, | ['A.M.'] = { 'A.M.', 'P.M.' }, | ||
})[amopt] or { 'am', 'pm' } | })[amopt] or { 'am', 'pm' } | ||
− | return value < 12 and ap[1] or ap[2] | + | return (spaces == '' and '' or ' ') .. (value < 12 and ap[1] or ap[2]) |
end | end | ||
end | end | ||
if code.field == 'year' then | if code.field == 'year' then | ||
− | if | + | 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 | if value >= 0 then | ||
sign = '' | sign = '' | ||
else | else | ||
− | |||
value = -value | value = -value | ||
end | end | ||
− | |||
− | |||
− | |||
− | |||
end | end | ||
+ | return spaces .. sign .. sformat(fmt, value) | ||
end | end | ||
− | return fmt and | + | return spaces .. (fmt and sformat(fmt, value) or value) |
end | end | ||
end | end | ||
− | local function replace_property(id) | + | 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] | local result = date[id] | ||
if type(result) == 'string' then | if type(result) == 'string' then | ||
− | + | return spaces .. result | |
− | |||
− | |||
− | |||
− | |||
end | end | ||
if type(result) == 'number' then | if type(result) == 'number' then | ||
− | return tostring(result) | + | return spaces .. tostring(result) |
end | end | ||
if type(result) == 'boolean' then | if type(result) == 'boolean' then | ||
− | return result and '1' or '0' | + | return spaces .. (result and '1' or '0') |
end | end | ||
-- This occurs, for example, if id is the name of a function. | -- This occurs, for example, if id is the name of a function. | ||
return nil | return nil | ||
− | |||
− | |||
− | |||
end | end | ||
local PERCENT = '\127PERCENT\127' | local PERCENT = '\127PERCENT\127' | ||
return (format | return (format | ||
:gsub('%%%%', PERCENT) | :gsub('%%%%', PERCENT) | ||
− | :gsub('%%{(%w+)}', replace_property) | + | :gsub('(%s*)%%{(%w+)}', replace_property) |
− | :gsub('%%(-?)(%a)', replace_code) | + | :gsub('(%s*)%%(-?)(%a)', replace_code) |
:gsub(PERCENT, '%%') | :gsub(PERCENT, '%%') | ||
) | ) | ||
end | end | ||
− | local function | + | local function _date_text(date, fmt, options) |
-- Return formatted string from given date. | -- Return formatted string from given date. | ||
− | |||
− | |||
− | |||
if type(fmt) ~= 'string' then | if type(fmt) ~= 'string' then | ||
− | fmt = '% | + | fmt = '%-d %B %-Y %{era}' |
if date.hastime then | if date.hastime then | ||
if date.second > 0 then | if date.second > 0 then | ||
− | fmt = | + | fmt = '%H:%M:%S ' .. fmt |
else | else | ||
− | fmt = | + | fmt = '%H:%M ' .. fmt |
end | end | ||
end | end | ||
− | return strftime(date, fmt, options | + | return strftime(date, fmt, options) |
end | end | ||
if fmt:find('%', 1, true) then | if fmt:find('%', 1, true) then | ||
Line 345: | Line 363: | ||
f = '%H:%M:%S' | f = '%H:%M:%S' | ||
elseif item == 'ymd' then | elseif item == 'ymd' then | ||
− | f = '%Y | + | f = '%Y-%m-%d %{era}' |
elseif item == 'mdy' then | elseif item == 'mdy' then | ||
− | f = '%B %-d, %Y%{era}' | + | f = '%B %-d, %-Y %{era}' |
elseif item == 'dmy' then | elseif item == 'dmy' then | ||
− | f = '%-d %B %Y%{era}' | + | f = '%-d %B %-Y %{era}' |
else | else | ||
return '(invalid format)' | return '(invalid format)' | ||
Line 418: | Line 436: | ||
end | end | ||
}) | }) | ||
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local function extract_date(text) | local function extract_date(text) | ||
Line 459: | Line 443: | ||
-- or return nothing if date is known to be invalid. | -- or return nothing if date is known to be invalid. | ||
-- Caller determines if the values in n are valid. | -- Caller determines if the values in n are valid. | ||
− | -- Dates of form d/m/y, m/d/y, y/m/d are rejected as ambiguous | + | -- 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 date, options = {}, {} | ||
local function extract_ymd(item) | local function extract_ymd(item) | ||
Line 537: | Line 525: | ||
end | end | ||
for item in text:gsub(',', ' '):gmatch('%S+') do | for item in text:gsub(',', ' '):gmatch('%S+') do | ||
− | |||
item_count = item_count + 1 | item_count = item_count + 1 | ||
if era_text[item] then | if era_text[item] then | ||
+ | -- Era is accepted in peculiar places. | ||
+ | if options.era then | ||
+ | return | ||
+ | end | ||
options.era = item | options.era = item | ||
elseif ampm_options[item] then | elseif ampm_options[item] then | ||
Line 574: | Line 565: | ||
end | end | ||
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 | end | ||
return date, options | 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 | end | ||
-- Metatable for some operations on dates. | -- 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) | __eq = function (lhs, rhs) | ||
-- Return true if dates identify same date/time where, for example, | -- Return true if dates identify same date/time where, for example, | ||
− | -- (-4712, 1, 1, 'Julian') == (-4713, 11, 24, 'Gregorian'). | + | -- 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, | end, | ||
__lt = function (lhs, rhs) | __lt = function (lhs, rhs) | ||
− | -- Return true if 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. | |
− | |||
− | if | ||
− | |||
− | |||
return lhs.jdz < rhs.jdz | return lhs.jdz < rhs.jdz | ||
end, | end, | ||
Line 611: | Line 694: | ||
value = self.jd - first + 1 -- day-of-year 1 to 366 | value = self.jd - first + 1 -- day-of-year 1 to 366 | ||
elseif key == 'era' then | elseif key == 'era' then | ||
− | -- Era text from year and options. | + | -- Era text (not a negative sign) from year and options. |
− | + | value = get_era_for_year(self.options.era, self.year) | |
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
elseif key == 'gsd' then | elseif key == 'gsd' then | ||
-- GSD = 1 from 00:00:00 to 23:59:59 on 1 January 1 AD Gregorian calendar, | -- GSD = 1 from 00:00:00 to 23:59:59 on 1 January 1 AD Gregorian calendar, | ||
Line 642: | Line 718: | ||
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: | --[[ Examples of syntax to construct a date: | ||
Line 649: | Line 729: | ||
Date('currentdate') | Date('currentdate') | ||
Date('currentdatetime') | Date('currentdatetime') | ||
− | |||
− | |||
Date('1 April 1995', 'julian') parse date from text | Date('1 April 1995', 'julian') parse date from text | ||
− | Date('1 April 1995 AD', 'julian') | + | 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('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 | function Date(...) -- for forward declaration above | ||
− | -- Return a table | + | -- 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 calendars = { julian = 'Julian', gregorian = 'Gregorian' } | ||
local result = { | local result = { | ||
− | |||
calname = 'Gregorian', -- default is Gregorian calendar | calname = 'Gregorian', -- default is Gregorian calendar | ||
hastime = false, -- true if input sets a time | hastime = false, -- true if input sets a time | ||
Line 666: | Line 748: | ||
minute = 0, | minute = 0, | ||
second = 0, | second = 0, | ||
− | month_days = | + | month_days = _month_days, |
− | + | options = make_option_table(), | |
− | + | text = _date_text, | |
− | |||
− | |||
− | |||
− | options = | ||
− | text = | ||
} | } | ||
local argtype, datetext | local argtype, datetext | ||
Line 684: | Line 761: | ||
elseif calendars[vlower] then | elseif calendars[vlower] then | ||
result.calname = calendars[vlower] | 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 | else | ||
local num = tonumber(v) | local num = tonumber(v) | ||
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end | end | ||
elseif argtype then | elseif argtype then | ||
− | return | + | return |
elseif type(v) == 'string' then | elseif type(v) == 'string' then | ||
if v == 'currentdate' or v == 'currentdatetime' or v == 'juliandate' then | if v == 'currentdate' or v == 'currentdatetime' or v == 'juliandate' then | ||
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end | end | ||
else | else | ||
− | return | + | return |
end | end | ||
end | end | ||
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set_date_from_numbers(result, | set_date_from_numbers(result, | ||
extract_date(datetext))) then | extract_date(datetext))) then | ||
− | return | + | return |
end | end | ||
elseif argtype == 'juliandate' then | elseif argtype == 'juliandate' then | ||
− | + | result.jd = numbers[1] | |
− | + | if not (numbers.n == 1 and set_date_from_jd(result)) then | |
− | + | return | |
− | |||
− | return | ||
end | end | ||
elseif argtype == 'currentdate' or argtype == 'currentdatetime' then | elseif argtype == 'currentdate' or argtype == 'currentdatetime' then | ||
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end | end | ||
result.calname = 'Gregorian' -- ignore any given calendar name | result.calname = 'Gregorian' -- ignore any given calendar name | ||
− | |||
elseif argtype == 'setdate' then | elseif argtype == 'setdate' then | ||
if not set_date_from_numbers(result, numbers) then | if not set_date_from_numbers(result, numbers) then | ||
− | return | + | return |
end | end | ||
− | + | elseif not is_copy then | |
− | return | + | return |
end | end | ||
return setmetatable(result, datemt) | return setmetatable(result, datemt) | ||
end | end | ||
− | + | function DateDiff(date1, date2) -- for forward declaration above | |
− | -- Return a table | + | -- 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 | local isnegative | ||
− | if date2 | + | if date1 < date2 then |
isnegative = true | isnegative = true | ||
date1, date2 = date2, date1 | date1, date2 = date2, date1 | ||
end | end | ||
− | -- It is known that date1 | + | -- It is known that date1 >= date2. |
local y1, m1 = date1.year, date1.month | local y1, m1 = date1.year, date1.month | ||
local y2, m2 = date2.year, date2.month | local y2, m2 = date2.year, date2.month | ||
− | local years, months, days = y2 - | + | local years, months, days = y1 - y2, m1 - m2, date1.day - date2.day |
if days < 0 then | if days < 0 then | ||
− | days = days + days_in_month( | + | days = days + days_in_month(y2, m2, date2.calname) |
months = months - 1 | months = months - 1 | ||
end | end | ||
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end, | end, | ||
} | } | ||
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end | end | ||
return { | return { | ||
− | + | _current = current, | |
− | |||
_Date = Date, | _Date = Date, | ||
− | + | _DateDiff = DateDiff, | |
− | + | _days_in_month = days_in_month, | |
− | |||
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− | |||
} | } |
Revision as of 04:58, 7 March 2016
Documentation for this module may be created at Module:Date/doc
-- 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, }