Singles' Day is on 11th of November and this year it's on the Wednesday. According to Wikipedia:
Chinese Singles' Day or Guanggun Jie (Chinese: 光棍节; pinyin: Guānggùn Jié; Wade–Giles: Kuang-kun chieh; literally: “bare sticks holiday”) is an entertaining festival widespread among young Chinese people, to celebrate the fact that they are proud of being single. The date, November 11th (11/11), is chosen because the number “1” resembles an individual that is alone. This festival has become the largest online shopping day in the world, with sales in Alibaba's sites Tmall and Taobao at US$5.8 billion in 2013, US$9.3 billion in 2014, US$14.3 billion in 2015 and over US$17.8 billion in 2016.
Many Australian and overseas stores are also running special promotions on this day. Here are OzBargain's collection of deals for the Singles' Day.