It’s a good idea to have your lights on anytime you’re driving, day or night, when you’re more visible to others there’s always a less chance of an accident. California State Law requires you to turn on your headlights half an hour after sunset and keep them on until half an hour before sunrise. In addition, you must use your headlights when it’s raining and/or fog and it’s necessary for you to use your windshield wipers continuously or when you have trouble seeing other cars.