The reason it IS light 20 hours a day is because of the unusually low angle of the sun on the horizon, keeping it in sight throughout much of the planet's asymetric parabola, while greatly weakening the strength of its rays (both infrared and ultraviolet a & b).
It ain't how long it's on you, it's how hard it hits you. You can burn in 18 minutes under the right (wrong?) conditions.
Good thought, just wrong.