Simple working equations are presented which allow for the treatment of time-dependent first-order electric and magnetic properties based on the linear response of the Kohn-Sham density matrix. They are generally applicable to existing nonrelativistic molecular density functional code implementations. This extends the formulas for frequency-dependent polarizabilities previously reported by other authors to include the cases of frequency-dependent optical rotation parameters and magnetic susceptibilities. An expression for the magnetic transition dipole moment is extracted from the results. Existing codes for excitation energies and polarizabilities can be easily extended to compute the optical rotation parameter and rotatory strengths. We further discuss possible extensions towards time-dependent current-density response.