FORTRAN julian day

subroutine juld(iy,im,id,ih,mn,jday)
integer iy,im,id,ih,mn
real day(12),jday
data day/31.,28.,31.,30.,31.,30.,31.,31.,30.,31.,30.,31./

if ( mod(iy,4).eq.0 .and. (mod(iy,100).ne.0
& .or. mod(iy,400).eq.0) ) then
day(2)=29.
endif

jday=0.

if (im-1.eq.0) then
jday=0.
else !if (im-1.eq.0) then
do i=1,im-1
jday=jday+day(i)
enddo
endif !if (im-1.eq.0) then
jday=jday+float(id) + (float(ih)/24.) + (float(mn)/1440.)

return
end