Please don’t be disheartened by training/non-training, this is not the focus.
There are rules that need to be followed by everybody in hospitals regarding safe working hours.
I would advise you to do the following:
Exception report, discuss with Consultant about this, as well as the Guardian of Safe Working, especially if this keeps happening on a regular basis. Discuss why do think this is happening, ask for advice, do not let this happen on and on.
The earlier you raise concerns the earlier some measures will be taken.
Try to finish your jobs before 5, if anything left handover to the evening on call doctor.
Please think about patients safety as well, as this is paramount, because the later you stay / or the more frequently, the higher the risk of doing a mistake that can result in harm/negligence etc. If something bad is to happen the first question will be why you haven’t raised this issue before.
Best wishes.