Automotive clears that are supplied by the large manufacturers, i.e. R-M, Dupont, Sherwin and Williams, Glasurit, ect. all have their clearing material designed with UV filters in them.
There are two types of car paint; the ones they use in the manufacturing process, and the ones that are used in the aftermarket industry that are generally used for repair work. The paint manufacturers supply both industries, but the products are different.
The ones they develop for manufacturing are formulated to be baked at high temperatures to achieve their durability, and the repair industry uses clears that are catalyzed with chemical hardeners.
Car paint, in general doesn't fade any more, and any manufactured car that shows early clear coat break down, is because the manufacturer has minimized the mil thickness to save money! Got this right out of the horse's mouth...

Automotive clears and their hardeners are generally glass clear, and somehow the chemists in the industry have designed UV filters into them, so I'm going to start some non-sprayed experiments.