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