No, it is always resume by 1200 on Off Peak (without the day) tickets, I typed completed when I meant to say resume! You can choose to break overnight on the Off Peak but you cannot make that choice with the Off Peak Day. In the highly unlikely event of the last northbound train from Derby going to Chesterfield and not on to Sheffield, then you could take that and break overnight and resume the next morning on an Off Peak Day. But, in reality, if you wanted to break overnight you'd need the Off Peak. But splitting the journey into two tickets would be far cheaper! So in this case the Off Peak is really pointless!