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 == 'JCAL' 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
-- 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 == 'JCAL' 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 == 'JCAL' then
limits = { -1931076.5, 5373557.5 }
elseif calname == 'GCAL' then
limits = { -1930999.5, 5373484.5 }
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 == 'JCAL' 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 date_text(date)
-- Return formatted string from given date.
if not date.isvalid then
return '(invalid)'
end
local time = ''
if date.hastime then
if date.second > 0 then
time = string.format(' %02d:%02d:%02d',
date.hour,
date.minute,
date.second
)
else
time = string.format(' %02d:%02d',
date.hour,
date.minute
)
end
end
local y = date.year
local sign = ''
if y < 0 then
sign = MINUS
y = -y
end
return string.format('%s%04d-%02d-%02d%s',
sign,
y,
date.month,
date.day,
time
)
end
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
-- Metatable for some operations on dates.
-- For Lua 5.1, __lt does not work if the metatable is an anonymous table.
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 == '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 == '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 == 'is_leap_year' then
value = is_leap_year(self.year, self.calname)
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')
]]
local function Date(...)
-- 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 = 'JCAL', Julian = 'JCAL', gregorian = 'GCAL', Gregorian = 'GCAL' }
local result = {
isvalid = false, -- false avoids __index lookup
calname = 'GCAL', -- 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,
text = date_text,
}
local numbers = collection()
local datetext
local argtype
for _, v in ipairs({...}) do
v = strip_to_nil(v)
if v == nil then
-- Ignore empty arguments after stripping so modules can directly pass template parameters.
elseif calendars[v] then
result.calname = calendars[v]
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 = 'GCAL' -- 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 == 'JCAL'
local calname = 'GCAL' -- 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,
}