You must use headlights when driving

Nighttime is the correct answer.

Explanation:

One must use headlights when driving at night, but we should use the headlights in such a way the we are able to balance to see the road ahead without blinding other drivers. If you are using high beam do not forget to switch to low beam when you are within 150 metres of a vehicle and when you are following another car.  Although passing at nighttime is legal, we should avoid it whenever possible. Also it is also legally required to turn on your headlights between 30 minutes before and after sunset and sunrise.