real*8 function yd2 ( yd, d )
!
!     Given a real*8 date (and fraction) of the form yyyyddd.dd,
!     and a positive or negative increment of days (and fraction),
!     return the real*8 date yd+d.
!
!     B. Knapp, 96.04.11
!
C
C     RCS DATA
C     
C     $Header$
C     
C     $Log$
C
C
      implicit none
!
      real*8 yd, d, jd
!
!     Convert input date to JD number, add increment, and convert
!     back to YD format:
      call yd2jd( yd, jd )
      call jd2yd( jd+d, yd2 )
      return
      end