Sky Box/Sphere??

Are there any official Specs for a Skybox? If so where?

Any good tutorials on making dynamic sky boxes?

@ Ostheim I found that you can change the texture underneath while still keeping all the basic functionality intact. You need a longlat hdri for the color and lighting. Everything else works the same. So you just adjust the parameters to make things move. Or you could create an animated hdri but that would take forever and seriously bog down your computer I think.