Keeping in mind that things can always change....
Christmas break is about 2 weeks and spring break is 10 days.
Summer break can vary depending upon what training you do and which details you are on. It could be 1-4 weeks. For example, last summer my son had 5 days off between graduation and his first summer assignment. Then he had 3 weeks off between his last summer assignment and when the academic year began. I don't know about this summer yet but it looks like he will get 4 weeks. It may be in one block or broken up.
For Thanksgiving this year cadets had a compressed schedule on Wed and were dismissed late morning. My plebe was dismissed at 1150 hrs. Formation was Sunday night at 1900 hrs.
Most plebes have their Term End Exams (TEE's) at the end of the week. My plebe's last TEE is Friday Dec 19th in the morning but cadets have to wait 3 hrs after the last TEE to be dismissed - at the earliest. There is a page full of rules depending on your transportation and when the last exam is. Formation is on January 4 again at 1900 hrs, I believe. If the upperclass finish their TEE's earlier in the week they will get 2+ weeks for leave.
Spring break for plebes is later than the upperclass because PPW is that weekend.
While the rest of the Corps is dismissed on March 13th, plebes must stay for PPW which is noon Friday to noon on Sunday. Formation is March 22 at 1900 hrs. Plebes still get a week, just not the two full weekends.
I think now with the compressed academic schedule the goal is to give every cadet 4 weeks leave every summer. The general idea is to break up summer into 3 - 4 week blocks of which one is leave.
Long weekends are basically gone from the schedule. Labor day was a three day weekend and President's day is a three day weekend and one may take a pass, if available but it is not leave.
A pass is used during the academic year to be gone overnight on weekends. Plebes are limited to one pass per semester, yearlings get two per semester, not sure about cows and firsties but they do increase each year. Cadets can earn more passes by tutoring, good perforamance, etc. Cadets in good standing also get one spirit pass per semester to go to an away sporting event.
Leave is Christmas break, spring break, and summer leave that all cadets get unless on restriction of some kind.