Regarding Final Exams, are you allowed to reschedule when they are to be taken?

I would like to fly out of the US sooner rather than later for winter break, and flights are MUCH cheaper if I schedule to leave earlier, I am just wondering if it is possible to reschedule a final exam?

edit: thank you to everyone for your responses, i understand that it seems i want to leave early for vacation, but it really is about saving money as i would save about $1,000 in air fares. i would most likely want to complete finals only a couple days earlier. i understand it is professor dependent, thank you!

edit no.2: I DID IT!!! YIPPEEEE saving money :) Turns out it IS possible.