Voyager actually returned in mid-2378. Remember them celebrating First Contact Day in Season 7?
But Neelix was the one throwing the party, so who says the anniversary was in Earth years?
As far as the Pocket novel continuity is concerned, "Endgame" happened at the end of 2377/start of 2378. There are alternate fan interpretations out there, but that's the way it is in the novelverse.