I really love that my cats can differentiate between a week day and the weekend.
Monday - Friday without fail, Owen wakes about an hour before the alarm, leaves the bedroom and sits on his chair in the dining room to wait until I get up and let him outside. (I know this from many occasions when my bloody bladder can't wait a mere 60 mins) Marley stays until the alarm goes off, and then he jumps up to get between me and the alarm clock (for a cat for is alarmed when you uncross your legs when sitting on the lounge I find it quite brave he gets so close to the blaring alarm.) Then he jumps off, waits outside the bathroom door until my shower is over, and then he gets ready to go outside.
But Saturdays and Sundays.... I've had the same wake up time for about 6 years for work, so if I'm very very lucky I sometimes sleep in on the weekend until 7am. (For work I wake at 5am, so even though 7am sounds early it's a whole two hour sleep in!!) Somehow the boys know. Owen stays on the bed sleeping until about 1130. I've even vacuumed the bedroom and he hasn't moved. Marley wakes, but he doesn't move until I do. And then he goes off to the spare room, where he sleeps until about 3pm.
And the reason that I know that they know it's the weekend, is because sometimes on weekends I've to set my alarm for something, and neither of them deviate from their weekend sleep-ins. They don't even get up for food on the weekends, whereas week days it's all about them getting food at 530 in the morning (And if I've been on holidays .... if it's Monday - Friday they will wake me up at 545 looking for food.)
For cats that are 7 in October, they act like teenagers.