I am retired, but as a guess I would say Xmas shutdown this year will be from 23 Dec to 1 Jan inclusive. You get the public holidays off, and the rest are taken as rec leave. They often include a "bonus" public holiday which cuts down on the rec leave required to be taken. It used to be, they couldn't force you to take rec leave, (this may have changed), so you just turned up on those days and did whatever (study, centre visit)