The last clause of Day's Undoing is ending the turn so any triggers that would have been put onto the stack are exiled instead. This is working as intended.
I have noted bug in 3 and 4 player games, when myriad trigger is resolved the tokens chosen are created but they do not enter attacking. I have not found any situation with myriad where this does not happen. This bug seems to appear both with granted myriad ability (blade of selves, Duke Ulder)...