Passage: Stan Wawrinka was the defending champion in men's singles but lost to four-time Australian Open champion Novak Djokovic in the semi-finals. Reigning women's champion Li Na did not defend her title, as she retired from professional tennis in September, 2014. Novak Djokovic won an Open Era record fifth men's singles crown by defeating Andy Murray in the final, and this was the third time they met each other in the final. Serena Williams won an Open Era record six women's singles championships by defeating Maria Sharapova in the final, and this was the second time they met each other in the final.Simone Bolelli and Fabio Fognini teamed up to win the men's doubles title for the first time over the team of Pierre-Hugues Herbert and Nicolas Mahut. Bethanie Mattek-Sands and Lucie Šafářová teamed up to win the women's doubles crown for the first time over the team of Chan Yung-jan and Zheng Jie. Martina Hingis and Leander Paes teamed up to win the mixed doubles title, it was the second for Hingis and third for Paes, over the defending champions Kristina Mladenovic and Daniel Nestor.

Question: When did she finally hang it up?
September, 2014