Cats are carpuscial not nocturnal.
I've no idea what that is, but ours are certainly not nocturnal.
We have a cat-flap and the only time ours go out (at night) is for a quick toilet - no more than 2 mins.
I suspect the nocturnal thing comes from the habit of "putting the cat out for the night".
Ours just sleep, wake up, stretch, see if there's anything to eat, potter about, clean, sleep etc.
They like to lay in the garden when the sun's out, but other than that, would much rather be inside (unless we're outside).