Use a red flashlight and check out the colors in the darkened room. Obviously everything would look red. The same principle applies to other sources. Incandescent light makes a room appear warm, fluorescent light makes objects look pale and flat, and daylight makes everything look true and natural. Since beginning of time daylight has only been available with the rising of the sun and disappears when the sun sets.
Daylight is defined as the combination of sunlight and skylight.