The rental periods are set and not subject to change. With prior negotiation with your landlord, it is possible to arrive after the beginning of the rental contract and/or to leave before the end of the rental contract. In any case, the rent has to be paid in full throughout the whole duration of the rental period regardless. Moving in/moving out outside of the agreed timeframe is not allowed. Rental contracts can neither be terminated or extended. Students need to check their study period and rental periods accordingly.