You know what you need to do to really fuck their day over. Go out late (after 12) at night way after they are asleep, and on the side of their house should be a huge level that controls the power, just flip it off wait about 3 hours then flip it back on with some gloves on, go back inside, and go to sleep. All their clocks should have reset back to 12:00 so they are now off by 3 hours. Will totally fuck up an appointments they have for the day. Then the next day just flip the power off and leave it off.