Officials with the ABC television network said Tuesday that World News anchor Charles Gibson will sign off for the last time on December 18th. The 66-year-old Gibson announced his impending retirement in September. Gibson began hosting World News in 2006, following a successful stint as co-host on Good Morning America. On December 21st, veteran ABC news journalist Diane Sawyer will become the new anchor for World News. Along with CBS’ Katie Couric — for the first time in history — two of the three leading network news anchors will be women.