Final answer:
Headlights should be used at nighttime, dusk, and dawn, and are generally not required during clear daytime conditions, though daytime running lights may still be used for increased visibility.
Step-by-step explanation:
Headlights must be used at specific times to ensure visibility and safety on the road. Generally, headlights should be used at nighttime, as well as during dusk and dawn when natural light is low. While daytime running lights are common and can help increase visibility during the day, especially in poor weather conditions, standard headlights are not typically required during clear daytime conditions unless specified by local laws.