Panderson, 1st, if the sailor/soldier is only requesting to go off base for the evening or weekend (even a long, holiday weekend) it is not leave, it's called liberty. Your sailor will know the difference quickly, leave requires advance notice, paperwork with okays from commanding officers, etc. Liberty is given most evenings after school is let out for the day unless they have mando (mandatory study hall) or duty. It is also what they get for the weekend (unless again, mando or duty, etc) if they wish to go off base overnight. If I remember correctly, extended liberty (overnight) is earned at Phase III which I think was about 6 weeks.

To qualify for leave the sailor must turn in a chit sheet several weeks to a few months in advance and must have accumulated enough days to cover the requested time off. Leave is vacation time, or family emergency time away from work. If your sailor has not earned enough working days to cover the leave time then they go "in the hole" which means they have to work those days back before taking leave again.

How much time they get off at holidays and whether or not they can leave is dependent on several factors ie: which school they are attending at the holiday, have they earned leave time, have they had any disciplinary actions against them, can they afford to get home and back, and if they are scheduled for duty during that time can they find someone to switch off with them so they don't have to pull watches. Even if the schools shut down for a week, the base continues to run so there still has to be security, duty drivers, etc. The likelihood of school shutting down for more than 4 days at Thanksgiving is slim and if the school were to have a lot of sailors on hold during that time they would still have to make a choice between taking time at Thanksgiving or taking time at Christmas.

Sorry but once they are in the fleet that's pretty much how it works. If they have leave at Thanksgiving, they must be back for Christmas and New Years. If they take Christmas, then they generally have to leave early Dec and be back before New Year's. Then there is the group that gets leave at New Year's. Unfortunately, there will probably be times your sailor will not be home for any of the big holidays especially the first couple of years. Once they have a bit of seniority they get better choices, but of course it requires planning in advance. The schools are not shut down for a month but you get the idea. Your sailor may well rather keep the leave time instead of spending it and use it before the 1st duty station. Especially if they are going overseas and won't be able to afford to come home for a year or more.  

You will learn the lingo and how it all works as time goes on. This is your adjustment period too. Once your sailor is in the fleet and possibly at sea, you might not be able to see him/her for several holidays. You just have to get used to it and remember they wanted to do this job. If you get the chance, go see your sailor at Dam Neck. They don't have to use the leave time and still get to see some family members. Enjoy them being stateside as long as possible, only a few by chance never go overseas or out to sea at all.