The Time Stop spell says:
This spell ends if one of the actions you use during this period, or any effects that you create during this period, affects a creature other than you or an object being worn or carried by someone other than you.
Does Animate Dead end Time Stop? It targets "a pile of bones or a corpse of a Medium or Small humanoid within range", which at least for a pile of bones counts as an object, not a creature, and creates a creature out of them, a Skeleton, but is he affecting a creature?
(Background: I am interested as Acererak in Tomb of Annhilation has both spells, so if he won initiative, he could possibly animate a number of skeletons under time stop, even though that might also not be enough to make the final fight challenging, if you go by How do you make the final battle in Tomb of Annihilation non-trivial?. His spell options for time stoppable spells seem extremely limited.).