Giant panda Tian Tian celebrates 20th birthday in U.S.

Giant panda Tian Tian enjoys birthday cake during a celebration for its 20th birthday at Smithsonian's National Zoo in Washington D.C., the United States, Aug. 27, 2017. The zoo held a celebration on Sunday for giant panda Tian Tian's 20th birthday. (Xinhua/Yin Bogu)