The date is well known to be the 3rd of Hearthfire (or the 8th according to in-game books, the wiki and the books are not in agreement on this, although showing up on the 3rd then the 8th would guarantee you see her one of those days), but the location hrm... one would have to assume it's either the Shadow Stone or back in the Twilight Sepulcher.
This I intend to discover sir. I do hope you aren't intentionally sending anyone on a goose chase here...
I dunno about her appearing, but I do know that "Nocturnal's Cloak" is not an in-game item. and while she apparently has an Actor, said character does not have a cloak, just some clothes and a hat that you can't get.