I have 3 Pokemon who are max friendship (the five hearts) in Pokemon Amie and I waited untill 8:30 but Uxie still isn't in the nameless cavern :( What am I doing wrong?
Actually it should be max friendship, and not affection, which is what the Amie hearts show.
Get 3 Pokemon that have been with you throughout your playthrough of the game and Uxie should appear.
Reddit thread - Uxie & Azelf not appearing