OP is probably a troll but I like explaining things so here it goes:
It depends if your program uses a night float system or a call system. My program is night float. We work 28 day blocks and switch services thereafter. We get 4 of 28 days off per ACGME rules. So it works out like this:
M-F juniors arrive at 6am, sign out at 5pm, leave around 6pm usually. Seniors arrive a little later (630) and leave earlier (515) unless operating. Most programs seem to start at 5am. However, they also end earlier than mine does. We never end earlier and often time stay past sign out. Example: This week I have stayed until 7pm and 10pm on different days. We tend to get a lot of add on cases through the ED that go late.
Sat/Sun x 2: arrive at 7am, sign out at 7pm. Most programs do this differently: one weekend you work a 24 Friday (7a to 7a), off Saturday, and a 12 Sunday (7a to 7p) and then the other weekend you work Saturday 24 hour 7a to 7p. Either way, you still end up working 24 hours on 2 weekends per month, weekend being defined as friday evening to sunday evening.
Other Sat/Sun x2: off
The advantage of night float is you get two golden weekends pretty consistently.
The disadvantage if you have to work nights, usually 2 to 3 blocks a year. This usually involves working Sunday to Thursday 5pm to 7am. You get 4 "weekends" off although you have to come in Sunday night and likely spend all Friday sleeping. This is because ACGME only allows 5 night float days in a row. But you are also working minimum 14 hours per shift instead of 12.
Also, most programs usually have a didactics day that messes things up a bit. On this day, 7am to 12pm is usually "protected time" meaning you go to lecture or training and you are not responsible for floor stuff. However, you may have to start rounding earlier on this day to stay on top of things and/or stay later after 12pm in order to catch up. If you're on night float, you still go to didactics after your night shift but are allowed to leave earlier, at 9am or 10am, for example, because of ACGME rules that mandate 8 hours off between shifts.
Hope this clarifies things. It's complicated.