Your relationship to the person on whom you are spying matters. If that person is your child or your employee, you have a lot more leeway when it comes to monitoring their activities. If you think someone is spying on you illegally, file a report with local law enforcement so they can investigate your case.
Most cats snooze around 16 hours per day. The majority of their sleep time, however, is much shorter than the typical seven hours or so that humans average at. night. Cats tend to sleep lightly, without going into a deep sleep.
Around 16 hours seems to be the average, but young kittens and senior cats can snooze even longer: around 18 hours a day. Many people believe their kittens are nocturnal and are awake and active all through the night. This is not true. Cats are crepuscular animals.