Description of the fortran package UAI2000.package (Ch. Bizouard, December 2002) In the frame of the UAI 2000 recommendations and IERS 2000 conventions, the IERS Earth Orientation Center proposes fortran subroutines (iau2000.package) in order to convert the UAI 1980 celestial pole offsets (dpsi,deps)_1980 to the UAI 2000 celestial pole offsets (dpsi,desp)_2000, (dX,dY)_2000 and conversely. (1) SUBROUTINE diff2000_1980(DMJD,dpsi,deps) -computes the differences dpsi_2000 - dspi_1980 deps_2000 - deps_1980 for a given modified julian date -It should be noticed that, in the current subroutine, the bias and drift between the ICRF and the dynamical reference frame associated with the precession-nutation model IAU 2000, is taken into account. These corrections, specified at the end of the subroutine, can be easily removed from the code. -2 subroutines called : arglunsol,argplan (2) SUBROUTINE dXdY_dpsideps(dmjd,cp1in,cp2in,cp1out,cp2out,opt) Transformation of the celestial pole offsets (dpsi,deps)_2000 to the celestial pole offsets (dX,dY)_2000 and inversely. PACKAGE LOCATION : ftp://hpiers.obspm.fr/eop-pc/models/uai2000.package ftp://hpiers.obspm.fr/eop-pc/models/uai2000.package.readme