Any closed, flat Riemannian manifold is finitely covered by the torus, by Bieberbach?s classical theorem. Similar classifications have been pursued for closed, Riemannian conformally flat manifolds, notably by Fried and Goldman, as well as for closed, flat Lorentzian manifolds, notably by Carrière and D?Albo. I will discuss current work with Nakyung Lee and Goldman towards classifying closed, Lorentzian conformally flat manifolds when they have nilpotent holonomy.