I'm assuming that you mean DEALERS' schedule. It totally depends upon the casino, but two of the most common schedules are:
1) 12:00 noon - 8:00pm; 8:00pm - 4:00am; 4:00am - 12:00 noon.
2) 10:00am - 6:00pm; 6:00pm - 2:00am; 2:00am - 10:00am.
These two schedules seem to be split up among 95% of all L.V. casinos, with the first schedule a little more prevalent than the second; and with the others there seems to be no rhyme or reason to their scheduling.
Bear in mind that even with the casinos that adhere to a strict schedule, they still will almost always have a myriad of split shifts. For example, the Venetian is on the 12:00 noon schedule, but they have dealers coming & going at 10:00, 11:00, 1:00, 2:00, and even 4:00; depending upon how busy they expect to be at the time.
Finn Dog is right about surveillance, they almost always stagger these guys exactly in the middle of the dealer's shifts.