Sakura can definitely tell when 7:00 rolls around. She comes and stares at me til I look, then starts with the little woofs and pawing the floor. If I ignore her still will start to bark. If I don't feed her dinner at exactly 7:00 she thinks will waste away. When we are at work at 5:30 she knows it is time to go home. And she starts barking like a crazy thing. My boss and co-workers think it is the funniest thing. She loves driving me nuts!
I lucked out with her trying to wake me on mornings though. She knows when the alarm goes off it is time to get up and will try her hardest to make me get out of bed. But if there is no alarms she sleeps.