aredna mayan date conversion bonus 1

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
)
,leapyears as
(
    select 1972 as yr
    union all
    select yr+case when (yr+4) % 100 = 0 and (yr+4) % 400 <> 0 then 8 else 4 end
    from leapyears
    where yr < 100000
)
,datediffs as
(
   select n,
          midx =   1856304
                  + (y-1970)*365
                  + case m when 1 then  0    when 5 then 120    when  9 then 243
                           when 2 then 31    when 6 then 151    when 10 then 273
                           when 3 then 59    when 7 then 181    when 11 then 304
                           when 4 then 90    when 8 then 212    when 12 then 334
                           end
                  + (d)
                  + ( select count(*) from leapyears where yr<y or (yr=y and m>2) )
   from pivotdates
)
,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
option (maxrecursion 32000)