It's the Mid Autumn or Harvest Moon Festival today, the 15th day of the 8th month of the Lunar calendar, it falls on September 27, 2015 this year.
Today is the Chinese Mid-Autumn Festival, more commonly known as the Harvest Moon Festival by people outside China. It is on the 15th day of the 8th month on the Lunar calendar. It is a festival celebrating harvest, similar to Thanksgiving in the US.
The 15th day of the 8th month on the Lunar calendar is the day with the brightest full moon during the entire year, thus this festival is also known as the Harvest Moon Festival.This Festival has a legend that includes a rabbit. Not as common as the other names, once a while it is also called the Rabbit Festival.
Thousands of years ago, there were nine suns that scorched the earth day and night continuously. The earth was in a plight of severe drought. A "hero", Hou-Yee, who was proficient in archery shot down eight of the nine suns, as a result he was crowned the king. Then Hou-Yee became a cruel dictator, wanting to live forever. He had miracle medicine made, with the help from a rabbit, for him that he would ingest and then he would live forever. His queen Churn-O, the most beautiful woman in the kingdom, did not want the people to suffer. She ingested all the miracle medicine, became very light and started flying. She took the rabbit with her and landed on the moon. The rabbit, Chinese referred to as "the Jade Rabbit", continuously make medicine in the moon until today. Churn-O and the Jade Rabbit live in the moon happily ever after.
Many years later, a tradition of eating "Moon Cake" was added to this festival. Here is a drawing of flying Churn-O with the Jade Rabbit on a moon cake advertisement.