Module:Date: Difference between revisions

    From Nonbinary Wiki
    (support date difference codes 'dhms' and 'hms')
    (Enhanced)
    Line 1: Line 1:
    -- 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 from date's time, where (0 <= fraction < 1)
    -- if the values are valid, but could be anything if outside range.
    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 fix_numbers(numbers, y, m, d, H, M, S, partial, hastime, calendar)
    -- Put the result of normalizing the given values in table numbers.
    -- The result will have valid m, d values if y is valid; caller checks y.
    -- The logic of PHP mktime is followed where m or d can be zero to mean
    -- the previous unit, and -1 is the one before that, etc.
    -- Positive values carry forward.
    local date
    if not (1 <= m and m <= 12) then
    date = Date(y, 1, 1)
    if not date then return end
    date = date + ((m - 1) .. 'm')
    y, m = date.year, date.month
    end
    local days_hms
    if not partial then
    if hastime and H and M and S then
    if not (0 <= H and H <= 23 and
    0 <= M and M <= 59 and
    0 <= S and S <= 59) then
    days_hms = hms({ hour = H, minute = M, second = S })
    end
    end
    if days_hms or not (1 <= d and d <= days_in_month(y, m, calendar)) then
    date = date or Date(y, m, 1)
    if not date then return end
    date = date + (d - 1 + (days_hms or 0))
    y, m, d = date.year, date.month, date.day
    if days_hms then
    H, M, S = date.hour, date.minute, date.second
    end
    end
    end
    numbers.year = y
    numbers.month = m
    numbers.day = d
    if days_hms then
    -- Don't set H unless it was valid because a valid H will set hastime.
    numbers.hour = H
    numbers.minute = M
    numbers.second = S
    end
    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
    local need_fix
    if y and m and d then
    date.partial = nil
    if 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
    if not date.want_fix then
    return
    end
    need_fix = true
    end
    elseif y and date.partial then
    if d or not (-9999 <= y and y <= 9999) then
    return
    end
    if m and not (1 <= m and m <= 12) then
    if not date.want_fix then
    return
    end
    need_fix = true
    end
    else
    return
    end
    if date.partial then
    H = nil  -- ignore any time
    M = nil
    S = nil
    else
    if H then
    -- It is not possible to set M or S without also setting H.
    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
    if date.want_fix then
    need_fix = true
    else
    return
    end
    end
    end
    date.want_fix = nil
    if need_fix then
    fix_numbers(numbers, y, m, d, H, M, S, date.partial, date.hastime, date.calendar)
    return set_date_from_numbers(date, numbers, options)
    end
    date.year = y    -- -9999 to 9999 ('n BC' → year = 1 - n)
    date.month = m  -- 1 to 12 (may be nil if partial)
    date.day = d    -- 1 to 31 (* = nil if partial)
    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]
    if not value then
    return nil  -- an undefined field in a partial date
    end
    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 '&nbsp;') .. (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 '&nbsp;') .. 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 if id is an undefined field in a partial date, or 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
    elseif date.partial then
    fmt = date.month and 'my' or 'y'
    else
    fmt = 'dmy'
    if date.hastime then
    fmt = (date.second > 0 and 'hms ' or 'hm ') .. fmt
    end
    end
    local function bad_format()
    -- For consistency with other format processing, return given format
    -- (or cleaned format if original was not a string) if invalid.
    return mw.text.nowiki(fmt)
    end
    if date.partial then
    -- Ignore days in standard formats like 'ymd'.
    if fmt == 'ym' or fmt == 'ymd' then
    fmt = date.month and '%Y-%m %{era}' or '%Y %{era}'
    elseif fmt == 'my' or fmt == 'dmy' or fmt == 'mdy' then
    fmt = date.month and '%B %-Y %{era}' or '%-Y %{era}'
    elseif fmt == 'y' then
    fmt = date.month and '%-Y %{era}' or '%-Y %{era}'
    else
    return bad_format()
    end
    return strftime(date, fmt, options)
    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
    return bad_format()
    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, sept = 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 >'
    if not is_date(date) then
    error('date:list: need a date (use "date:list()" with a colon)', 2)
    end
    local list = { text = _list_text }
    if date.partial then
    return list
    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.
    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(newdate, 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 = {}, {}
    if text:sub(-1) == 'Z' then
    -- Extract date/time from a Wikidata timestamp.
    -- The year can be 1 to 16 digits but this module handles 1 to 4 digits only.
    -- Examples: '+2016-06-21T14:30:00Z', '-0000000180-00-00T00:00:00Z'.
    local sign, y, m, d, H, M, S = text:match('^([+%-])(%d+)%-(%d%d)%-(%d%d)T(%d%d):(%d%d):(%d%d)Z$')
    if sign then
    y = tonumber(y)
    if sign == '-' and y > 0 then
    y = -y
    end
    if y <= 0 then
    options.era = 'BCE'
    end
    date.year = y
    m = tonumber(m)
    d = tonumber(d)
    H = tonumber(H)
    M = tonumber(M)
    S = tonumber(S)
    if m == 0 then
    newdate.partial = true
    return date, options
    end
    date.month = m
    if d == 0 then
    newdate.partial = true
    return date, options
    end
    date.day = d
    if H > 0 or M > 0 or S > 0 then
    date.hour = H
    date.minute = M
    date.second = S
    end
    return date, options
    end
    return
    end
    local function extract_ymd(item)
    -- Called when no day or month has been set.
    local y, m, d = item:match('^(%d%d%d%d)%-(%w+)%-(%d%d?)$')
    if y then
    if date.year then
    return
    end
    if m:match('^%d%d?$') then
    m = tonumber(m)
    else
    m = month_number(m)
    end
    if m then
    date.year = tonumber(y)
    date.month = m
    date.day = tonumber(d)
    return true
    end
    end
    end
    local function extract_day_or_year(item)
    -- Called when a day would be valid, or
    -- when a year would be valid if no year has been set and partial is set.
    local number, suffix = item:match('^(%d%d?%d?%d?)(.*)$')
    if number then
    local n = tonumber(number)
    if #number <= 2 and n <= 31 then
    suffix = suffix:lower()
    if suffix == '' or suffix == 'st' or suffix == 'nd' or suffix == 'rd' or suffix == 'th' then
    date.day = n
    return true
    end
    elseif suffix == '' and newdate.partial and not date.year then
    date.year = n
    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]  -- caller checked this is not nil
    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('&nbsp;', ' '):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 extract_day_or_year(item) then
    return
    end
    elseif extract_month(item) then
    options.format = 'mdy'
    elseif extract_ymd(item) then
    options.format = 'ymd'
    elseif extract_day_or_year(item) then
    if date.day then
    options.format = 'dmy'
    end
    else
    return
    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.
    if lhs.partial then
    -- Adding to a partial is not supported.
    -- Can subtract a date or partial from a partial, but this is not called for that.
    return
    end
    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' (with optional sign).
    -- Fractions like '3.25d' are accepted for the units which are handled as days.
    local sign, numstr, id = rhs:match('^%s*([+-]?)([%d%.]+)%s*(%a+)$')
    if sign then
    if sign == '-' then
    is_sub = not (is_sub and true or false)
    end
    local y, m, days
    local num = tonumber(numstr)
    if not num then
    return
    end
    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
    days = num * 7
    elseif is_prefix(id, 'days') then
    days = num
    elseif is_prefix(id, 'hours') then
    days = num / 24
    elseif is_prefix(id, 'minutes', 3) then
    days = num / (24 * 60)
    elseif is_prefix(id, 'seconds') then
    days = num / (24 * 3600)
    else
    return
    end
    if days then
    return do_days(days)
    end
    if numstr:find('.', 1, true) then
    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
    local full_date_only = {
    dayabbr = true,
    dayname = true,
    dow = true,
    dayofweek = true,
    dowiso = true,
    dayofweekiso = true,
    dayofyear = true,
    gsd = true,
    juliandate = true,
    jd = true,
    jdz = true,
    jdnoon = true,
    }
    -- Metatable for a date's calculated fields.
    local datemt = {
    __index = function (self, key)
    if rawget(self, 'partial') then
    if full_date_only[key] then return end
    if key == 'monthabbr' or key == 'monthdays' or key == 'monthname' then
    if not self.month then return end
    end
    end
    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 called only if lhs and rhs have the same type and the same metamethod.
    if lhs.partial or rhs.partial then
    -- One date is partial; the other is a partial or a full date.
    -- The months may both be nil, but must be the same.
    return lhs.year == rhs.year and lhs.month == rhs.month and lhs.calendar == rhs.calendar
    end
    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 called only if lhs and rhs have the same type and the same metamethod.
    if lhs.partial or rhs.partial then
    -- One date is partial; the other is a partial or a full date.
    if lhs.calendar ~= rhs.calendar then
    return lhs.calendar == 'Julian'
    end
    if lhs.partial then
    lhs = lhs.partial.first
    end
    if rhs.partial then
    rhs = rhs.partial.first
    end
    end
    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.
    -- A partial date has a valid year, however its month may be nil, and
    -- its day and time fields are nil.
    -- Field partial is set to false (if a full date) or a table (if a partial date).
    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 vlower == 'partial' then
    newdate.partial = true
    elseif vlower == 'fix' then
    newdate.want_fix = true
    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.partial = v.partial
    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(newdate, datetext)) then
    return
    end
    elseif argtype == 'juliandate' then
    newdate.partial = nil
    newdate.jd = jd_number
    if not set_date_from_jd(newdate) then
    return
    end
    elseif argtype == 'currentdate' or argtype == 'currentdatetime' then
    newdate.partial = nil
    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
    if newdate.partial then
    local year = newdate.year
    local month = newdate.month
    local first = Date(year, month or 1, 1, newdate.calendar)
    month = month or 12
    local last = Date(year, month, days_in_month(year, month), newdate.calendar)
    newdate.partial = { first = first, last = last }
    else
    newdate.partial = false  -- avoid index lookup
    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 integer values from diff as specified by code, except that
    -- each integer may be a list of two integers for a diff with a partial date, or
    -- return nil if the code is not supported.
    -- If want round, the least significant unit is rounded to nearest whole unit.
    -- For a duration, an extra day is added.
    local wantround, wantduration, wantrange
    if type(options) == 'table' then
    wantround = options.round
    wantduration = options.duration
    wantrange = options.range
    else
    wantround = options
    end
    if not is_diff(diff) then
    local f = wantduration and 'duration' or 'age'
    error(f .. ': need a date difference (use "diff:' .. f .. '()" with a colon)', 2)
    end
    if diff.partial then
    -- Ignore wantround, wantduration.
    local function choose(v)
    if type(v) == 'table' then
    if not wantrange then
    -- Example: Date('partial', 2005) - Date('partial', 2001) gives
    -- diff.years = { 3, 4 } to show the range of possible results.
    -- If do not want a range, choose the second value as more expected.
    return v[2]
    end
    end
    return v
    end
    if code == 'ym' or code == 'ymd' then
    if not wantrange and diff.iszero then
    -- This avoids an unexpected result such as
    -- Date('partial', 2001) - Date('partial', 2001)
    -- giving diff = { years = 0, months = { 0, 11 } }
    -- which would be reported as 0 years and 11 months.
    return 0, 0
    end
    return choose(diff.partial.years), choose(diff.partial.months)
    end
    if code == 'y' then
    return choose(diff.partial.years)
    end
    return nil
    end
    local extra_days = wantduration and 1 or 0
    if code == 'wd' or code == 'w' or code == 'd' then
    local offset = wantround and 0.5 or 0
    local days = diff.age_days + extra_days
    if code == 'wd' or code == 'd' then
    days = floor(days + offset)
    if code == 'd' then
    return days
    end
    return floor(days/7), days % 7
    end
    return floor(days/7 + offset)
    end
    local H, M, S = diff.hours, diff.minutes, diff.seconds
    if code == 'dh' or code == 'dhm' or code == 'dhms' or code == 'h' or code == 'hm' or code == 'hms' then
    local days = floor(diff.age_days + extra_days)
    local inc_hour
    if wantround then
    if code == 'dh' or code == 'h' then
    if M >= 30 then
    inc_hour = true
    end
    elseif code == 'dhm' or code == 'hm' then
    if S >= 30 then
    M = M + 1
    if M >= 60 then
    M = 0
    inc_hour = true
    end
    end
    else
    -- Nothing needed because S is an integer.
    end
    if inc_hour then
    H = H + 1
    if H >= 24 then
    H = 0
    days = days + 1
    end
    end
    end
    if code == 'dh' or code == 'dhm' or code == 'dhms' then
    if code == 'dh' then
    return days, H
    elseif code == 'dhm' then
    return days, H, M
    else
    return days, H, M, S
    end
    end
    local hours = days * 24 + H
    if code == 'h' then
    return hours
    elseif code == 'hm' then
    return hours, M
    end
    return hours, M, S
    end
    if wantround then
    local inc_hour
    if code == 'ymdh' or code == 'ymwdh' then
    if M >= 30 then
    inc_hour = true
    end
    elseif code == 'ymdhm' or code == 'ymwdhm' then
    if S >= 30 then
    M = M + 1
    if M >= 60 then
    M = 0
    inc_hour = true
    end
    end
    elseif code == 'ymd' or code == 'ymwd' or code == 'yd' or code == 'md' then
    if H >= 12 then
    extra_days = extra_days + 1
    end
    end
    if inc_hour then
    H = H + 1
    if H >= 24 then
    H = 0
    extra_days = extra_days + 1
    end
    end
    end
    local y, m, d = diff.years, diff.months, diff.days
    if extra_days > 0 then
    d = d + extra_days
    if d > 28 or code == 'yd' then
    -- Recalculate in case have passed a month.
    diff = diff.date1 + extra_days - diff.date2
    y, m, d = diff.years, diff.months, diff.days
    end
    end
    if code == 'ymd' then
    return y, m, d
    elseif code == 'yd' then
    if y > 0 then
    -- It is known that diff.date1 > diff.date2.
    diff = diff.date1 - (diff.date2 + (y .. 'y'))
    end
    return y, floor(diff.age_days)
    elseif code == 'md' then
    return y * 12 + m, d
    elseif code == 'ym' or code == 'm' then
    if wantround then
    if d >= 16 then
    m = m + 1
    if m >= 12 then
    m = 0
    y = y + 1
    end
    end
    end
    if code == 'ym' then
    return y, m
    end
    return y * 12 + m
    elseif code == 'ymw' then
    local weeks = floor(d/7)
    if wantround then
    local days = d % 7
    if days > 3 or (days == 3 and H >= 12) then
    weeks = weeks + 1
    end
    end
    return y, m, weeks
    elseif code == 'ymwd' then
    return y, m, floor(d/7), d % 7
    elseif code == 'ymdh' then
    return y, m, d, H
    elseif code == 'ymwdh' then
    return y, m, floor(d/7), d % 7, H
    elseif code == 'ymdhm' then
    return y, m, d, H, M
    elseif code == 'ymwdhm' then
    return y, m, floor(d/7), d % 7, H, M
    end
    if code == 'y' then
    if wantround and m >= 6 then
    y = y + 1
    end
    return y
    end
    return nil
    end
    local function _diff_duration(diff, code, options)
    if type(options) ~= 'table' then
    options = { round = options }
    end
    options.duration = true
    return _diff_age(diff, code, options)
    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
    if rawget(self, 'partial') then
    local function jdz(date)
    return (date.partial and date.partial.first or date).jdz
    end
    value = jdz(self.date1) - jdz(self.date2)
    else
    value = self.date1.jdz - self.date2.jdz
    end
    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
    local iszero = false
    if date1 < date2 then
    isnegative = true
    date1, date2 = date2, date1
    elseif date1 == date2 then
    iszero = true
    end
    -- It is known that date1 >= date2 (period is from date2 to date1).
    if date1.partial or date2.partial then
    -- Two partial dates might have timelines:
    ---------------------A=================B--- date1 is from A to B inclusive
    --------C=======D-------------------------- date2 is from C to D inclusive
    -- date1 > date2 iff A > C (date1.partial.first > date2.partial.first)
    -- The periods can overlap ('April 2001' - '2001'):
    -------------A===B------------------------- A=2001-04-01  B=2001-04-30
    --------C=====================D------------ C=2001-01-01  D=2001-12-31
    local function zdiff(date1, date2)
    local diff = date1 - date2
    if diff.isnegative then
    return { years = 0, months = 0 }
    end
    return diff
    end
    local function getdate(date, which)
    return date.partial and date.partial[which] or date
    end
    local maxdiff = zdiff(getdate(date1, 'last'), getdate(date2, 'first'))
    local mindiff = zdiff(getdate(date1, 'first'), getdate(date2, 'last'))
    local years, months
    if maxdiff.years == mindiff.years then
    years = maxdiff.years
    if maxdiff.months == mindiff.months then
    months = maxdiff.months
    else
    months = { mindiff.months, maxdiff.months }
    end
    else
    years = { mindiff.years, maxdiff.years }
    end
    return setmetatable({
    date1 = date1,
    date2 = date2,
    partial = { years = years, months = months },
    isnegative = isnegative,
    iszero = iszero,
    age = _diff_age,
    duration = _diff_duration,
    }, diffmt)
    end
    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,
    partial = false,  -- avoid index lookup
    years = years,
    months = months,
    days = days,
    hours = H,
    minutes = M,
    seconds = S,
    isnegative = isnegative,
    iszero = iszero,
    age = _diff_age,
    duration = _diff_duration,
    }, diffmt)
    end
    return {
    _current = current,
    _Date = Date,
    _days_in_month = days_in_month,
    }

    Revision as of 15:23, 10 October 2017

    Documentation for this module may be created at Module:Date/doc
    Retrieved from "https://nonbinary.wiki/index.php?title=Module:Date&oldid=30269"