Preferred days to START the travel are: Monday, Thursday and Saturday. Friday is not preferred (due to the commitment of the compulsory congregation prayer).
There's something on this; If its possible one should start their journey on thursday because it is a Sunnah to start on a thursday. (Ashi’a-tul-Lam’aat, vol. 5, pp.161) If its possible to travel at night then one should travel at night because the journey is completed faster.
i believe there are hadith that mention that beginning travels on certains days is recommended. does anyone know these hadith?