New Vegas 2281, 'Fall of Shady Sands' 2277 according to the show. Sorry but jog on with that nonsense. Show literally has Shady Sands being nuked BEFORE the events of New Vegas. Just look at the damn chalkboard.
Maximus also confirms this retcon when he says the nuke dropped '20 years ago'..
And of course, Lucy is told her mum died during the famine of 2277 BUT she was in fact turned into a Ghoul by the nuke.
Tired of all you show fanboys ignoring the poor writing and retcons, all the evidence is there in the very show. It retcons NV and a lot of the lore. End of dicussion.