We describe a detailed photon correlation Fourier spectroscopy (PCFS) study of a single CdSe/ZnS nanocrystal at 10 K. PCFS provides the temporal and spectral resolution that is necessary for such a fast spectrally diffusing emitter. In the emitter spectrum, we distinguish a main 6 µeV zero-phonon line, the one- and twolongitudinal- optical-phonon replica, and the longitudinal-acoustic-phonon pedestal. We determine the spectral diffusion amplitude as a function of time for timescales from 20 µs to 200 ms and propose an interpretation for the two observed regimes.