Effect of Sunlight / UV rays on mugs

Ok, I'm not sure if this is a dumb question. I've got my mugs on a shelf in my office that sun shines into and right on them. Do ceramic glazes fade or discolor over time if exposed to bright light?

I'd imagine anything would fade or discolor under bright sunlight. I know I did...

I know that car paint fades in sun but this is more like colored glass. Stained glass windows take a beating 24/7 cause thats what they do.