The Gemara told that Rav Joseph's wife used to kindle the Sabbath lights late (just before nightfall). Rav Joseph told her that it was taught in a Baraita that the words of "the pillar of cloud by day, and the pillar of fire by night, departed not," teach that the pillar of cloud overlapped the pillar of fire, and the pillar of fire overlapped the pillar of cloud. So she thought of lighting the Sabbath lights very early. But an elder told her that one may kindle when one chooses, provided that one does not light too early (as it would not evidently honor the Sabbath) or too late (later than just before nightfall).