aredna mayan date conversion

declare @i varchar(999) = '3 1 1 1970 20 7 1988 12 12 2012';

;with parseinput as
(
   select n = cast(substring(@i,1,charindex(' ',@i)-1) as int)*3,
          i = cast(substring(@i,charindex(' ',@i)+1,999)+' ' as varchar(100)),
          x = 0,
          t = 'x'
   union all
   select n = n-1,
          i = cast(substring(i,charindex(' ',i)+1,999) as varchar(100)),
          x = cast(substring(i,1,charindex(' ',i)-1) as int),
          t = case n%3 when 0 then 'd' when 2 then 'm' else 'y' end
   from parseinput
   where n > 0
)
,pivotdates as
(
   select n = n/3,
          d = max(case when t = 'd' then x else 0 end),
          m = max(case when t = 'm' then x else 0 end),
          y = max(case when t = 'y' then x else 0 end)
   from parseinput
   where t <> 'x'
   group by n/3
)
,convertdates as
(
   select n, dt = dateadd(day,d-1,dateadd(month,m-1,dateadd(year,y-1900,0)))
   from pivotdates
)
,datediffs as
(
   select n, dt, midx = datediff(day,'2012-12-21',dt)+144000*13
   from convertdates
)
,convertmayan as
(
   select n,
          baktun = cast(midx/20/20/18/20      as varchar(9)),
          katun  = cast(midx/20/18/20    % 20 as varchar(9)),
          tun    = cast(midx/20/18       % 20 as varchar(9)),
          winal  = cast(midx/20          % 18 as varchar(9)),
          kin    = cast(midx             % 20 as varchar(9))
   from datediffs
)
select baktun+'.'+katun+'.'+tun+'.'+winal+'.'+kin
from convertmayan
order by n desc