return message('mt-date-wrong-order')
end
return from_en(dateDifference(parms))
end  
local function isFake(args)
-- Some templates have TemplateData with an auto value like "".
-- Return true if that appears to be the case so the caller can output nothing rather than an error.
return args[1] == 'YYYY'
end  
local function bda
-- Implement Template:Birth date and age.
local args = :getParent.args
if isFake(args) then
return ''
end
local options = {
missing1 = 'mt-need-valid-bd',
noMissing = true,
single = true,
}
local date = getDates(, options)
if type(date) == 'string' then
return date -- error text
end
local Date = getExports
local diff = Date('currentdate') - date
if diff.isnegative or diff.years > 150 then
return message('mt-invalid-bd-age')
end
local disp = mtext['txt-bda-disp']
local show = 'y'
if diff.years < 2 then
disp = 'disp_age'
if diff.years == 0 and diff.months == 0 then
show = 'd'
else
show = 'm'
end
end
local result = substituteParameters(
mtext['txt-bda'],
date:text('%-Y-%m-%d'),
from_en(date:text(dateFormat(args))),
from_en(dateDifference({
diff = diff,
show = show,
abbr = 'abbr_off',
disp = disp,
sep = 'sep_space',
}))
local warnings = tonumber(.args.warnings)
if warnings and warnings > 0 then
local good = {
df = true,
mf = true,
day = true,
day1 = true,
month = true,
month1 = true,
year = true,
year1 = true,
}
local invalid
local imax = options.textdates and 1 or 3
for k, _ in pairs(args) do
if type(k) == 'number' then
if k > imax then
invalid = tostring(k)
break
end
else
if not good[k] then
invalid = k
break
end
end
end
if invalid then
result = result .. message('mt-bad-param1', invalid)
end
end
return result
end  
local function dda
-- Implement Template:Death date and age.
local args = :getParent.args
if isFake(args) then
return ''
end
local options = {
missing1 = 'mt-need-valid-dd',
missing2 = 'mt-need-valid-bd2',
noMissing = true,
partial = true,
}
local date1, date2 = getDates(, options)
if type(date1) == 'string' then
return date1
end
local diff = date1 - date2
if diff.isnegative then
return message('mt-dd-wrong-order')
end
local Date = getExports
local today = Date('currentdate') + 1 -- one day in future allows for timezones
if date1 > today then
return message('mt-dd-future')
end
local years
if diff.partial then
years = diff.partial.years
years = type(years) == 'table' and years[2] or years
else
years = diff.years
end
if years > 150 then
return message('mt-invalid-dates-age')
end
local fmt_date, fmt_ymd
if date1.day then -- y, m, d known
fmt_date = dateFormat(args)
fmt_ymd = '%-Y-%m-%d'
elseif date1.month then -- y, m known; d unknown
fmt_date = '%B %-Y'
fmt_ymd = '%-Y-%m-00'
else -- y known; m, d unknown
fmt_date = '%-Y'
fmt_ymd = '%-Y-00-00'
end
local sortKey
local sortable = translateParameters.sortable[args.sortable]
if sortable then
local value = (date1.partial and date1.partial.first or date1).jdz
sortKey = makeSort(value, sortable)
end
local result = (sortKey or '') .. substituteParameters(
mtext['txt-dda'],
date1:text(fmt_ymd),
from_en(date1:text(fmt_date)),
from_en(dateDifference({
diff = diff,
show = 'y',
abbr = 'abbr_off',
disp = mtext['txt-dda-disp'],
range = 'dash',
sep = 'sep_space',
}))
local warnings = tonumber(.args.warnings)
if warnings and warnings > 0 then
local good = {
df = true,
mf = true,
}
local invalid
local imax = options.textdates and 2 or 6
for k, _ in pairs(args) do
if type(k) == 'number' then
if k > imax then
invalid = tostring(k)
break
end
else
if not good[k] then
invalid = k
break
end
end
end
if invalid then
result = result .. message('mt-bad-param1', invalid)
end
end
return result
end  
local function dateToGsd
-- Implement Template:Gregorian serial date.
-- Return Gregorian serial date of the given date, or the current date.
-- The returned value is negative for dates before 1 January 1 AD
-- despite the fact that GSD is not defined for such dates.
local date = getDates(, { wantMixture=true, single=true })
if type(date) == 'string' then
return date
end
return tostring(date.gsd)
end  
local function jdToDate
-- Return formatted date from a Julian date.
-- The result includes a time if the input includes a fraction.
-- The word 'Julian' is accepted for the Julian calendar.
local Date = getExports
local args = :getParent.args
local date = Date('juliandate', args[1], args[2])
if date then
return from_en(date:text)
end
return message('mt-need-jdn')
end  
local function dateToJd
-- Return Julian date (a number) from a date which may include a time,
-- or the current date ('currentdate') or current date and time ('currentdatetime').
-- The word 'Julian' is accepted for the Julian calendar.
local Date = getExports
local args = :getParent.args
local date = Date(args[1], args[2], args[3], args[4], args[5], args[6], args[7])
if date then
return tostring(date.jd)
end
return message('mt-need-valid-ymd-current')
end  
local function timeInterval
-- Implement Template:Time interval.
-- There are two positional arguments: date1, date2.
-- The default for each is the current date and time.
-- Result is date2 - date1 formatted.
local Date = getExports
local args = :getParent.args
local parms = {
extra = makeExtra(args),
wantDuration = yes(args.duration),
range = yes(args.range) or (args.range == 'dash' and 'dash' or nil),
wantSc = yes(args.sc),
}
local fix = yes(args.fix) and 'fix' or ''
local date1 = Date(fix, 'partial', stripToNil(args[1]) or 'currentdatetime')
if not date1 then
return message('mt-invalid-start')
end
local date2 = Date(fix, 'partial', stripToNil(args[2]) or 'currentdatetime')
if not date2 then
return message('mt-invalid-end')
end
parms.diff = date2 - date1
for argname, translate in pairs(translateParameters) do
local parm = stripToNil(args[argname])
if parm then
parm = translate[parm]
if parm == nil then -- test for nil because false is a valid setting
return message('mt-bad-param2', argname, args[argname])
end
parms[argname] = parm
end
end
if parms.round then
local round = parms.round
local show = parms.show
if round ~= 'on' then
if show then
if show.id ~= round then
return message('mt-conflicting-show', args.show, args.round)
end
else
parms.show = translateParameters.show[round]
end
end
parms.round = true
end
return from_en(dateDifference(parms))
end  
local function templateGeneric
local name = .args.template
if not name then
return message('mt-template-x')
end
return ageGeneric(:newChild{title = mw.title.new(name, 10), args = .args})
end  
return {
age_generic = ageGeneric, -- can emulate several age templates
birth_date_and_age = bda, -- Template:Birth_date_and_age
death_date_and_age = dda, -- Template:Death_date_and_age
gsd = dateToGsd, -- Template:Gregorian_serial_date
extract = dateExtract, -- Template:Extract
jd_to_date = jdToDate, -- Template:?
JULIANDAY = dateToJd, -- Template:JULIANDAY
time_interval = timeInterval, -- Template:Time_interval
[''] = templateGeneric -- same as age_generic, but can be invoked directly
}