Module:Date
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)
-- Return nil if text is nil or is an empty string after trimming.
-- If text is a non-blank string, return its content after trimming.
-- Otherwise return text (convenient when accessed via another module).
if type(text) == 'string' then
local result = text:match("^%s*(.-)%s*$")
if result == '' then
return nil
end
return result
end
if text == nil then
return nil
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 = similar, but fractional part is zero at 00:00:00
-- 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
if not date.isvalid then
return 0, 0 -- always return numbers to simplify usage
end
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 date_part = date.day + floor((153*m + 2)/5) + 365*y + offset
local time_part, zbias
if date.hastime then
time_part = (date.hour + (date.minute + date.second / 60) /60) / 24 - 0.5
zbias = 0
else
time_part = 0
zbias = -0.5
end
local jd = date_part + time_part
return jd, jd + zbias
end
local function set_date_from_jd(date)
-- Set the fields of table date from its Julian date field.
-- 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
date.isvalid = false
return
end
date.isvalid = true
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)
end
local function make_option_table(options)
-- If options is a string, return a table with its settings.
-- Otherwise return options (it should already be a table).
if type(options) == 'string' then
-- Example: 'am:AM era:BC'
local result = {}
for item in options:gmatch('%S+') do
local lhs, rhs = item:match('^(%w+):(.*)$')
if lhs then
result[lhs] = rhs
end
end
return result
end
return options
end
local function strftime(date, format, options)
-- Return date formatted as a string using codes similar to those
-- in the C strftime library function.
if not date.isvalid then
return '(invalid)'
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', field = 'day' },
m = { fmt = '%02d', field = 'month' },
Y = { fmt = '%04d', field = 'year' },
H = { fmt = '%02d', field = 'hour' },
M = { fmt = '%02d', field = 'minute' },
S = { fmt = '%02d', field = 'second' },
j = { fmt = '%03d', field = 'doy' },
I = { fmt = '%02d', field = 'hour', special = 'hour12' },
p = { field = 'hour', special = 'am' },
X = { fmt = '%02d:%02d:%02d', field = 'hour', special = 'hms' },
['-d'] = { fmt = '%d', field = 'day' },
['-m'] = { fmt = '%d', field = 'month' },
['-Y'] = { fmt = '%d', field = 'year' },
['-j'] = { fmt = '%d', field = 'doy' },
}
options = make_option_table(options or date.options)
local amopt = options.am
local eraopt = options.era
local function replace_code(id)
local code = codes[id]
if code then
local fmt = code.fmt
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 == 'hms' then
return string.format(fmt, value, date.minute, date.second)
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 value < 12 and ap[1] or ap[2]
end
end
if code.field == 'year' then
if eraopt == 'BCMINUS' or eraopt == 'BCNEGATIVE' then
local sign
if value >= 0 then
sign = ''
else
sign = eraopt == 'BCMINUS' and MINUS or '-'
value = -value
end
return sign .. string.format(fmt, value)
end
if value <= 0 then
value = 1 - value
end
end
return fmt and string.format(fmt, value) or value
end
end
local function replace_property(id)
local result = date[id]
if type(result) == 'string' then
if id == 'era' and result ~= '' then
-- Assume era follows a date.
return ' ' .. result
end
return result
end
if type(result) == 'number' then
return tostring(result)
end
if type(result) == 'boolean' then
return 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('%%{(%w+)}', replace_property)
:gsub('%%(-?%a)', replace_code)
:gsub(PERCENT, '%%')
)
end
local function date_text(date, fmt, options)
-- Return formatted string from given date.
if not (type(date) == 'table' and date.isvalid) then
return '(invalid)'
end
if type(fmt) ~= 'string' then
fmt = '%Y-%m-%d'
if date.hastime then
if date.second > 0 then
fmt = fmt .. ' %H:%M:%S'
else
fmt = fmt .. ' %H:%M'
end
end
return strftime(date, fmt, options or { era = 'BCMINUS' })
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 date_component(named, positional, component)
-- Return the first of the two arguments (named like {{example|year=2001}}
-- or positional like {{example|2001}}) that is not nil and is not empty.
-- If both are nil, return the current date component, if specified.
-- This translates empty arguments passed to the template to nil, and
-- optionally replaces a nil argument with a value from the current date.
named = strip_to_nil(named)
if named then
return named
end
positional = strip_to_nil(positional)
if positional then
return positional
end
if component then
return current[component]
end
return nil
end
local era_text = {
-- options.era = { year<0 , year>0 }
['BCMINUS'] = { MINUS , '' },
['BCNEGATIVE'] = { '-' , '' },
['BC'] = { 'BC' , '' },
['B.C.'] = { 'B.C.' , '' },
['BCE'] = { 'BCE' , '' },
['B.C.E.'] = { 'B.C.E.', '' },
['AD'] = { 'BC' , 'AD' },
['A.D.'] = { 'B.C.' , 'A.D.' },
['CE'] = { 'BCE' , 'CE' },
['C.E.'] = { 'B.C.E.', 'C.E.' },
}
-- Metatable for some operations on dates.
-- For Lua 5.1, __lt does not work if the metatable is an anonymous table.
local Date -- forward declaration
local datemt = {
__eq = function (lhs, rhs)
-- Return true if dates identify same date/time where, for example,
-- (-4712, 1, 1, 'Julian') == (-4713, 11, 24, 'Gregorian').
return lhs.isvalid and rhs.isvalid and lhs.jdz == rhs.jdz
end,
__lt = function (lhs, rhs)
-- Return true if lhs < rhs.
if not lhs.isvalid then
return true
end
if not rhs.isvalid then
return false
end
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 from year and options.
local eraopt = self.options.era
local sign
if self.year == 0 then
sign = (eraopt == 'BCMINUS' or eraopt == 'BCNEGATIVE') and 2 or 1
else
sign = self.year > 0 and 2 or 1
end
value = era_text[eraopt][sign]
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,
}
--[[ 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')
LATER: Following are not yet implemented:
Date('currentdate', H, M, S) current date with given time
Date('1 April 1995', 'julian') parse date from text
Date('1 April 1995 AD', 'julian') AD, CE, BC, BCE (using one of these sets a flag to do same for output)
Date('04:30:59 1 April 1995', 'julian')
]]
function Date(...) -- for forward declaration above
-- Return a table to hold a date assuming a uniform calendar always applies (proleptic).
-- If invalid, return an empty table which is regarded as invalid.
local calendars = { julian = 'Julian', gregorian = 'Gregorian' }
local result = {
isvalid = false, -- false avoids __index lookup
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 = function (self, month)
return days_in_month(self.year, month, self.calname)
end,
-- 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.'
options = { am = 'am', era = 'BC' },
text = date_text,
}
local numbers = collection()
local datetext
local argtype
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]
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 numbers.n > 0 then
return {}
end
-- TODO Parse datetext to extract y,m,d,H,M,S.
elseif argtype == 'juliandate' then
if numbers.n == 1 then
result.jd = numbers[1]
set_date_from_jd(result)
else
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
result.isvalid = true
elseif argtype == 'setdate' then
if not (3 <= numbers.n and numbers.n <= 6) then
return {}
end
local y, m, d = numbers[1], numbers[2], numbers[3]
if not (-9999 <= y and y <= 9999 and 1 <= m and m <= 12 and
1 <= d and d <= days_in_month(y, m, result.calname)) then
return {}
end
local H = numbers[4]
if H then
result.hastime = true
else
H = 0
end
local M = numbers[5] or 0
local S = numbers[6] or 0
if not (0 <= H and H <= 23 and
0 <= M and M <= 59 and
0 <= S and S <= 59) then
return {}
end
result.year = y -- -9999 to 9999; '1 BC' → year = 0; 'n BC' → year = 1 - n
result.month = m -- 1 to 12
result.day = d -- 1 to 31
result.hour = H -- 0 to 59
result.minute = M -- 0 to 59
result.second = S -- 0 to 59
result.isvalid = true
else
return {}
end
return setmetatable(result, datemt)
end
local function DateDiff(date1, date2)
-- Return a table to with the difference between the two given dates.
-- Difference is negative if the second date is older than the first.
-- TODO Replace with something using Julian dates?
-- Who checks for isvalid()?
-- Handle calname == 'Julian'
local calname = 'Gregorian' -- TODO fix
local isnegative
if date2 < date1 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 = y2 - y1, m2 - m1, date2.day - date1.day
if days < 0 then
days = days + days_in_month(y1, m1, 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
local function message(msg, nocat)
-- Return formatted message text for an error.
-- Can append "#FormattingError" to URL of a page with a problem to find it.
local anchor = '<span id="FormattingError" />'
local category
if not nocat and mw.title.getCurrentTitle():inNamespaces(0, 10) then
-- Category only in namespaces: 0=article, 10=template.
category = '[[Category:Age error]]'
else
category = ''
end
return anchor ..
'<strong class="error">Error: ' ..
msg ..
'</strong>' ..
category .. '\n'
end
local function age_days(frame)
-- Return age in days between two given dates, or
-- between given date and current date.
-- This code implements the logic in [[Template:Age in days]].
-- Like {{Age in days}}, a missing argument is replaced from the current
-- date, so can get a bizarre mixture of specified/current y/m/d.
local args = frame:getParent().args
local date1 = Date(
date_component(args.year1 , args[1], 'year' ),
date_component(args.month1, args[2], 'month'),
date_component(args.day1 , args[3], 'day' )
)
local date2 = Date(
date_component(args.year2 , args[4], 'year' ),
date_component(args.month2, args[5], 'month'),
date_component(args.day2 , args[6], 'day' )
)
if not (date1.isvalid and date2.isvalid) then
return message('Need valid year, month, day')
end
local sign = ''
local result = date2.jd - date1.jd
if result < 0 then
sign = MINUS
result = -result
end
return sign .. tostring(result)
end
local function age_ym(frame)
-- Return age in years and months between two given dates, or
-- between given date and current date.
local args = frame:getParent().args
local fields = {}
for i = 1, 6 do
fields[i] = strip_to_nil(args[i])
end
local date1, date2
if fields[1] and fields[2] and fields[3] then
date1 = Date(fields[1], fields[2], fields[3])
end
if not (date1 and date1.isvalid) then
return message('Need valid year, month, day')
end
if fields[4] and fields[5] and fields[6] then
date2 = Date(fields[4], fields[5], fields[6])
if not date2.isvalid then
return message('Second date should be year, month, day')
end
else
date2 = Date('currentdate')
end
return DateDiff(date1, date2):age_ym()
end
local function gsd_ymd(frame)
-- Return Gregorian serial date of the given date, or the current date.
-- Like {{Gregorian serial date}}, a missing argument is replaced from the
-- current date, so can get a bizarre mixture of specified/current y/m/d.
-- This also accepts positional arguments, although the original template does not.
-- The returned value is negative for dates before 1 January 1 AD despite
-- the fact that GSD is not defined for earlier dates.
local args = frame:getParent().args
local date = Date(
date_component(args.year , args[1], 'year' ),
date_component(args.month, args[2], 'month'),
date_component(args.day , args[3], 'day' )
)
if date.isvalid then
return tostring(date.gsd)
end
return message('Need valid year, month, day')
end
local function ymd_from_jd(frame)
-- Return formatted date from a Julian date.
-- The result is y-m-d or y-m-d H:M:S if input includes a fraction.
-- The word 'Julian' is accepted for the Julian calendar.
local args = frame:getParent().args
local date = Date('juliandate', args[1], args[2])
if date.isvalid then
return date:text()
end
return message('Need valid Julian date number')
end
local function ymd_to_jd(frame)
-- Return Julian date (a number) from a date (y-m-d), or datetime (y-m-d H:M:S),
-- or the current date ('currentdate') or current datetime ('currentdatetime').
-- The word 'Julian' is accepted for the Julian calendar.
local args = frame:getParent().args
local date = Date(args[1], args[2], args[3], args[4], args[5], args[6], args[7])
if date.isvalid then
return tostring(date.jd)
end
return message('Need valid year/month/day or "currentdate"')
end
return {
age_days = age_days,
age_ym = age_ym,
_Date = Date,
days_in_month = days_in_month,
gsd = gsd_ymd,
JULIANDAY = ymd_to_jd,
ymd_from_jd = ymd_from_jd,
ymd_to_jd = ymd_to_jd,
}