Charlie Gibson will anchor his final "World News" broadcast Friday, Dec. 18. "World News" EP Jon Banner made the announcement on the WorldNewser blog.

We're going to spend a good deal of time during his final week on the air looking back at the stories Charlie covered, hearing again from some of the remarkable people he interviewed, and paying tribute to our friend and colleague, and the enormous contribution he has made to ABC News over the last three decades.

Gibson announced in September that he would be retiring from ABC News. David Westin, the president of the news division, had announced that Diane Sawyer would begin anchoring the broadcast in January. This afternoon an ABC News spokeswoman told TVNewser the timeline has been moved up a bit and that Sawyer will begin anchoring, "very shortly after Charlie's last broadcast."