If default settings blood moon will happen on night 42. Unless your saying you have played to day 40 with out having any blood moons and you have not turned them off In settings?
I played with blood moons every 7 days I turned zombie spawning off for a couple in game days to do some building when I turned it on I haven't gotten a hord night blood moon or hord night hordes there should have been two since I had turned zombie spawning back on and there hasn't