A user's laptop monitor dims every evening.

The most likely cause of a laptop screen dimming consistently in the evening is an ambient light/adaptive brightness feature. Many laptops include an ambient light sensor that automatically changes screen brightness based on room lighting conditions. As natural light decreases later in the day, the sensor detects a darker environment and reduces brightness to save power and reduce eye strain. Because this behavior occurs at a predictable time (evening) and the user can temporarily correct it by manually increasing brightness, it strongly points to automatic brightness control rather than a hardware failure.

Changing the Ambient light setting (disabling adaptive brightness/auto-brightness) provides a permanent fix by preventing the system from adjusting brightness in response to lighting changes. While battery/power plans can also dim displays to conserve energy, that usually correlates with running on battery power or specific power-saving modes—not a consistent evening pattern. Graphics settings typically affect resolution, scaling, or driver features and are not the primary control for time-of-day dimming behavior. Scheduled tasks could theoretically run display-related scripts, but that is uncommon compared to built-in ambient light adaptation. Therefore, adjusting the ambient light/adaptive brightness setting is the best CompTIA A+ answer.