Comments about time domain techniques in electromagnetics

Nowadays, electromagnetic wave propagation and scattering are studied directly in the time-domain, whereas previously one consldered sine-wave excitations and Fourier transformations into the frequencydomain. Time-domain approaches are certainly much closer to the physical reality, but how do they deal with propagation within (or with scattering from) material media, since material properties are dispersive (frequency-dependant), at least over parts of the frequency spectrum? It is not obvious that timedomain approaches can determine the resulting distortion of the signal.