Every placement, be it community or ward will have an Off-Duty of sorts (some are actual folders and others are being digitalised) which is the schedule for that placement’s staff including us as students. These should be released at least a week in advance to allow you to make travel plans etc. but that sometimes needs to be chased up.
Generally you work the same shifts as your mentor but if this isn’t possible it should be identified who you’ll be working with to make sure you’re supported and you know who to go to if you have an issue whilst you’re in practice.
Different years have different requirements for how you spend your hours on placement which can affect the off-duty, for example in 2nd and 3rd year the NMC requires you to have evidence of exposure to 24 hour care (aka night shifts) but there is no longer a specific necessity of a certain number of shifts. However you should consult your course handbook for year on year updates of the requirements from the NMC and the University.