Methods to calculate energies of excited states or excitation energies, respectively, have already been discussed in detail in our original review . As the two principle ways to calculate excitation energies, difference-based methods of ∆SCF-DFT type as well as linear-response time-dependent density functional theory transferred to the subsystem DFT context have been mentioned in that context, even though the former approach was only briefly touched. In the mean time, both classes of methods have been considerably