USNA Leave and Liberty
SRHSMOM, your mid/cadet will eventually be able to take you to school on the difference between leave and liberty. Think you are talking about "leave periods" here, when a mid/cadet can leave their SA, go wherever, wear civilian clothes, etc., and be on break from SA routine. Liberty is the temporary and relatively local ability to leave SA, while following all regulations applicable to uniform and privileges for their class, and go into town or have the coveted overnight liberty for a weekend away.
I can speak to USNA. Your mid will have to do the homework to figure out when he/she is free to leave their SA on leave periods. At USNA, on the Wednesday before Thanksgiving, they will usually start classes earlier so mids can get out midday. They have to be back at a specified time on Sunday. Christmas/winter holiday, they can usually leave after their last exam, which, at USNA, will fall in the weeks immediately after the Army-Navy game. They have to be back by a specified time after the New Year. Spring break at Navy usually falls in March. Departure on Friday following LMO (last military obligation), return on the Sunday a week later.
Inter-sessional leave periods may be granted at the end of spring semester, following exams and before mids have to report back for various commitments. This could be briefings for summer training, Commissioning Week commitments. For plebes, Sea Trials, Herndon Monument, etc.
Summer training will consist of various mandatory and elective summer training blocks, with usually about 3 weeks leave squeezed in anywhere between June and August. Some mids choose to take voluntary summer school to ease their academic load or find a fun internship; some may be in involuntary summer school because of academic struggles, so some may not have leave at all. Mids cycle in and out of the Academy in between training blocks all summer long. If you are local, they might get a few nights home during the block changeover. Otherwise, they stay in Bancroft Hall or at sponsor's home between back-to-back blocks. Lots of fluidity in the summer, and each mid's schedule is different.
Reform of the Brigade is a specified date and time in August when everyone has to be back.
No matter what Academy, your mid/cadet will get plenty of briefs on the mechanics of the leave periods. Make sure he/she is absolutely confident of when they can leave and when they have to be back before booking airfare.
This has been the pattern for the last 10 years or so. Fellow parents can provide additional insight for your SA.