Actually, thinking about this, I made a mistake. Voyager isn't pointing its antenna at earth at that instant. It's actually pointing it to where the earth WILL be in 16 to 20 hours. Technically, that is probably no more difficult but my statement is more accurate.
From the distance of Voyager, I doubt it makes any difference where Earth is for pointing the antenna. As in, it is pointing to the same spot no matter the day or season. They probably dial in an inertial coordinate and that is it.
