What is the legal definition of “lighting up time”

1. The time period of natural lighting conditions, when there is no need to have the vehicle lights turned on
2. Correct answer: The night time or any other time of the day in which visibility conditions are poor due to weather conditions.
3. The time period in which the vehicle’s lights must be turned on while driving in a freeway
4. The night time period, between sunset and sunrise

Why'Poor visibility' means night time and any other time when you can't see well: fog, heavy rain, a dust storm. It is not limited to night.