  This paper deals with time stepping schemes for the Cahn--Hilliard equation
with three different types of dynamic boundary conditions. The proposed schemes
of first and second order are mass-conservative and energy-dissipative and --
as they are based on a formulation as a coupled system of partial differential
equations -- allow different spatial discretizations in the bulk and on the
boundary. The latter enables refinements on the boundary without an adaptation
of the mesh in the interior of the domain. The resulting computational gain is
illustrated in numerical experiments.
