Cats thrive on routine and often form repeatable daily habits. If your cat jumps on your lap at the same time every day, doing so likely helps them keep track of the time of day.
Cats also take note of our routines and habits, too. If you leave the house or sit at your desk for work at the same time each day, they’ll be aware. Over time, they learn how long their humans are typically away and when they tend to return, which helps them build a sense of what time it is.
Your cat might also be aware of the times you usually wake up and go to bed, eat your meals, take your shower, or sit down in front of the TV. If you feed your cat when you wake up in the morning and again when returning home, this will also help them get a sense of time each day.
The more you keep to a routine, the more it helps your cat work out the time.