Module:Updated

local Date = require('Module:Date')._Date
local current = require('Module:Date')._current

local p = {}

function p.main(frame)
	local day
	
	if frame.args[1] then
		local success, result = pcall(function() return Date(frame.args[1]):text('dmy') end)
		if success then 
			day = result
		else
			error('Invalid date format in Template:Update.')
		end
	else
		day = Date(current.year, current.month, current.day):text('dmy') + '[[Category:Pages using updated template with missing date]]'
	end
	
	--check for extra args
	local extra = ''
	if frame.args[3] and mw.title.getCurrentTitle() == 0 then
		extra = '[[Category:Pages using updated template with unknown parameters]]'
	end
	
	return string.format(": ''As of %s%s%s''", day, frame.args[2] or '', extra)
end

return p
Usage
