Arrowhead Medicine is 6AM to approx 4PM depending on how many patients are on your service. Call is q4 and can last till noon the next day. Thursday calls obviously are the best (weekend and half of Friday off) whereas Saturday calls suck (No weekend at all).
Arrowhead Surgery is approx 4-4:30AM till 5PM depending on how much floor work you have thereafter. Call is approx q7 (four/month), but can vary since there really is no regimented call schedule. Therefore you can have as crappy as q3, or as relaxed as q7. This is by far the busiest rotation hours-wise, but it was also the most fun.
Arrowhead Peds...well there is currently a change in staffing going on there right now so I really can't say how it's going to be once you're on rotations. For right now, it depends on which service in Peds that you're on. Newborn is two weeks, 8-2, with one person staying till 5 thereafter. Peds Wards is 6AM to 3-5PM with the same setup with one person staying. THERE IS NO CALL. Clinic is where the brunt of your work will come from. there it's 8-5 and God help you if you leave earlier. It's not gonna happen.
Arrowhead OBGYN- Haven't had it yet, so this is based on word of mouth. There is no order since patient turnover is super high. If not in Surgery, Labor & Delivery, or Prep, you are in clinic. There are short calls and night float is the only time that requires you to be there overnight. It's busy from day one. Could you imagine doing a Pap smear when you have no idea what you're looking for.
So that's the short rundown for at least Arrowhead, probably the best hospital in our schools choice of rotations to learn.
Hope it helps.