If you drive your car between 11pm and 5am your driving rating will be affected as driving at night does carry more risk (i.e. the ability to anticipate and see hazards ahead, night time vision etc). However, don't forget there are other factors in your driving you can influence to achieve a good driver rating and this doesn't mean you're unable to achieve a safe driver rating. You should aim to drive extra carefully and focus on your accelerating, braking, cornering and speed when driving during these times.