Nighttime driving is considered to be one hour after sunset or 12 midnight whichever happens earlier up to one hour before sunrise or 5 AM depending on which is later. There may be some differences in the rules regarding night time driving depending on where you live but the specification mentioned above is the most common that is being followed by people in most parts of the world.
There are some people who will not be allowed to drive at night unless they have already completed their certification of driving for 50 hours or more at night. This is a certification that you may need to get depending on where you live.