Plebes don't get a significant break until Thanksgiving. Then it's usually Wed after last class until 1800 Sunday. Sometimes, if the football team does well, plebes might get Saturday night liberty (i.e., until sometime Sunday) after a game. Depends on the Dant and Supe.
Christmas break is after last exam until around Jan 2nd (depending on the day of the week Jan. 1 falls). They get a week in March for spring break. Of course, being allowed to take leave depends on being in a satisfactory status in terms of grades, conduct, and physical education. Also, some mids will have watch (duty) during breaks. Unfortunately, it generally falls to those who live near Annapolis and/or those unsat.
Upper class get a certain number of "weekends" each semester, depending on their level of seniority.
First summer is plebe summer. The second summer involves about a month on a Yard Patrol Craft and/or a sailboat, a month on a real Navy ship working as an enlisted person and about a month of leave. Third summer includes 2-3 wks of summer school for all, about a month visiting Jax, New London and Quantico to learn about Navy Air, Subs and USMC, and another several weeks doing any number of things. 3-4 weeks of leave.
Final summer involves a month on a Navy ship as a junior officer (I believe those wanting to go Marines do a stint at Quantico), and a month doing leadership (commanding a Yard Patrol craft or sailboat, working Plebe Summer detail, etc.).
After graduation, mids get a month of "basket leave" and then either report to a school or an interim command.