Hurrah! Keeping down the spoilers!

50th Anniversary to be Simulcast Worldwide

Quoting The Sun:

The 3D episode goes out here on November 23 at 8pm on BBC1, so fans in LA will watch at noon while it airs in Sydney at 6am the next day.

That means here in Eastern Time it should air on BBCAmerica at 3 pm. Thank goodness that's a Saturday. I honestly would have taken off from work.