subroutine jlt 
     i           (ntd,
     m            jday,
     o            mo,nday)
c
c     + + + PURPOSE + + +
c     Given the day of the year (Julian date) determine the month
c     and day of the month.
c
c     + + + ARGUMENT DECLARATIONS + + +
      integer ntd,jday,mo,nday
c
c     + + + ARGUMENT DEFINITIONS + + +
c     ntd         - number of days in year (365; 366 if leap year and
c                    iopt=3, 5, 6)
c     jday        - Julian date; ie, day of the year.
c     mo          - The current month (1=Jan, 2=Feb...).
c     nday        - The day of the current month.
c
c     + + + LOCAL VARIABLES + + +
      integer nn(12)
      integer kday, j, ndflag
c
c     + + + LOCAL DEFINITIONS + + +
c     nn          - Number of days in each month (non-leap year).
c
c     + + + DATA INITIALIZATIONS + + +
      data nn/31,28,31,30,31,30,31,31,30,31,30,31/
c
c     + + + END SPECIFICATIONS + + +
c
c ---- Adjust for Leap Year.
      if(ntd.eq.366) then
        nn(2) = 29
      else
        nn(2) = 28
      endif
      kday = jday
c
c ---- Find the month.
      j = 0
 10   continue
        j = j + 1
        jday = jday -nn(j)
        ndflag = 0
        if (jday.le.0) then
          nday = jday +nn(j)
          ndflag = 50
        endif
      if(ndflag.eq.0 .and. j.lt.12) goto 10
c
      jday = kday
      mo = j
c
      return
      end