From what I've seen and heard: Domestic cats tend to be irregular in their sleeping habits, and there can be big differences between individual cats.
Some cats are very regular in their sleeping habits, have a bed or more where they regularly sleep, and they sleep at regular times.
Other cats are completely irregular - where, when changes from one day to the next.
Some cats have periods when they are very regular, followed by periods when they are completely unpredictable.
One of our cats has periods where she comes in by 11P M, goes to sleep and sleeps through until 5.30 AM. And so for a week or so. Followed by some completely irregular days when she is out all night. And then another regular week. And so on.
This one is sterilized - and perhaps whether the cat is sterilized/castrated plays a role in the cat's sleeping and other habits.