FWIW, the AmEx Plat card lounge access benefit when flying DL was changed at least several years ago from "within 24 hours" to "same day." I would therefore tend to believe that the DL same day rule for SkyTeam ElitePlus flying on a SkyTeam international itinerary really does mean same day, although an overnight flight seems to give two days worth of lounge access providing that nonDL lounges aren't being used as arrivals lounges (and of course providing that the airport setup permits you to get to the door of the lounge).