I want to fade some large prints just with keeping the print under bright italian summer sunlight.

Which (digital) printing process, paper,.. would you normally not recommend if it`s about saving the print of desaturation, paling, fading?
What would you think how long it takes for a noticeable change?

In best case, the print should be stable after keeping it out of sunlight. (But that could be done with UV protecting glas and just hanging the print indoor I think)

I`ve noticed, that just advertisement posters for outdoor use have a quite poor color and brightness fastness.