Franklin D. Roosevelt wouldn't travel on Friday the 13th.
(The fear of Friday the 13th is called paraskevidekatriaphobia, a word derived from the concatenation of the Greek words Paraskeví (Παρασκευή) (meaning Friday), and dekatreís (δεκατρείς) (meaning thirteen), attached to phobía (φοβία) (meaning fear). The term triskaidekaphobia, fear of the number 13, derives from the Greek words "tris", meaning 'three', "kai", meaning 'and', and "deka", meaning 'ten'. the whole word means three and ten. I'm not sure what the fear of pronouncing those phobias is called.)