c
ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
c
      function idate2iyd(imo,ida,iyr)
      dimension ndmon(12)
c                 J  F  M  A  M  J  J  A  S  O  N  D
      data ndmon/31,28,31,30,31,30,31,31,30,31,30,31/
c
c given iyr,imo,ida, convert to iyd (yyddd):
c
      if (ichdate(imo,ida,iyr).ne.0) then
        write(6,"('>>> idate2iyd: bad idate iyr,imo,ida=',3i3)")
     +    iyr,imo,ida
        idate2iyd = 0
        return
      endif
      ndmon(2) = 28
      if (mod(iyr,4).eq.0) ndmon(2) = 29
      iday = 0
      do i=1,imo-1
        iday = iday+ndmon(i)
      enddo
      idate2iyd = iyr*1000+iday+ida
      return
      end