For example, I like to train mine to accept me providing scritches (petting) with my feet and for them to be equally comfortable with using foot as hand
We didn't so much teach this trick, as he learned it on his own, but we got an automatic feeder for him to help us with his diet. It feeds him 6x per day, and since we're no longer the ones giving him food, he has stopped begging us for food at all hours.
In any case, a few months ago, we noticed him in the dining room, staring at the grandfather clock. Then the clock chimed, and he ran over to the feeder and stared at it until a few seconds later, when it dispensed the food. He doesn't do this, except around feeding time.
So, it's just pavlovian: he's learned to associate the clock chime with the feeder, and has a general idea when feeding time is based on how hungry he is. Still, it's a neat party trick to tell guests we have a cat who can read a clock and tell time.
My cat can almost definitely tell time within about 2 minuts. At least for a specific time of day.
He gets canned food the same time every day, and will remind me I've yet to feed him at most 2 minuts after (unless he's asleep).
The only clocks I have in the house are digital, and none makes a sound. It takes him a few days to adjust moving to and form daylight savings time, and the change is gradual. He does this after changing apartments, so it's not some noise form the outside. I have no explanation other than he can tell time.