cbegin documentation
c library date:        28-nov-1983
c function name:       doy_date
c source location:     dra0:[lee.netlib]doydate.for
c function type:       integer*4
c function reference:  i = doy_date(yrdoy)
c purpose:             to convert the date in the form yyddd to the
c                   form mmddyy
c
c arguments:
c name            type            i/o      definition
c ----            ----            ---      ----------
c yrdoy            integer*4      i      date in form yyddd
c
c returned function values:  date in form mmddyy
c
c restrictions:  1) doy_date must be typed integer*4 in calling program.
c             2) a "1900" year is assumed
c
c error conditions:  none
c
c entry points:  none
c
c external references:  idysyr - returns number of days in a given year
c
c development history:
c   developed 29-nov-1983, bcss/barry lee
c
cend documentation
c
      integer*4 function doy_date(yrdoy)
      implicit integer*4 (a-z)
      integer m(12)
      data m/31,59,90,120,151,181,212,243,273,304,334,365/
      yr=yrdoy/1000
      doy=yrdoy-1000*yr
      leap=idysyr(yr+1900)-365
      do i=1,12
        if(i.lt.2)then
          day=m(i)
        else
          day=m(i)+leap
        end if
        if(doy.le.day)then
          mon=i
          if(mon.eq.1)then
            j=0
          else
            j=m(i-1)
            if(mon.gt.2)j=j+leap
          end if
          day=doy-j
          doy_date=yr+100*(day+100*mon)
          return
        end if
      end do
      doy_date=0
      return
      end