How can the existing nutation correction time series be converted to the new X, Y angles and vice versa?

The conversion is such that : X=X_mod + dX; Y=Y_mod + dY, with dX= dpsi*sin(epsilon_0) and dY=deps, X_mod and Y_mod being the values provided by the expressions for X and Y as function of time, dpsi and deps the nutation corrections and epsilon_0 the obliquity of the ecliptic at J2000.