local p = {}

	--{{PAGENAME}}
	local pagename        = mw.title.getCurrentTitle().text
	local pgnm_d          = string.match(pagename, '%d+')
	local BC              = string.match(pagename, ' BC ') or
	                        string.match(pagename, ' BC$')
		--timespan
	local pgnm_decade     = string.match(pagename, '%d+0s')
	local pgnm_century    = string.match(pagename, 'century')
	local pgnm_millennium = string.match(pagename, 'millennium')
		--frominof

function p.error(msg)
	return '<strong class=\"error\">'..msg..'</strong>'
end

function p.sort_years(frame)
	-- param: 1,d,digit , 2,n,nod
	local args_d = frame.args[1] or frame.args.d or frame.args.digit
	local args_n = frame.args[2] or frame.args.n or frame.args.nod

	-- var d=digit, nod=number of digit
	local   d = tonumber( pgnm_d   or args_d )
	local nod = tonumber( args_n ) or 4

	-- if century/millennium = 2digits
	  if( pgnm_century or pgnm_millennium ) then nod = 2 end

	local sortkey = ( type(d)~='number' )
		 and p.error('sort: no digits found..')
		 or  
			( d<0  or  BC and 0<d ) -- 'BC' → '-'
			 and -10000 + math.abs(d) -- minus:e.g.100→(space/minus)-9900
			 or  string.format('%0'..nod..'d', d)

	return sortkey
end

return p