When a domestic cat is allowed to roam freely, it is out of place. Cats are better suited for living in the wild than say,domestic dogs, but when they are out they are part of the food chain.
As mentioned above, the local predators are a variable, but a car will make quick work of a cat. Most places people live, have cars.
Other animals, toxins, and a cat’s curiosity, can kill them.
I guess I’m saying neither daytime, nor nighttime are the “safest.”