The Mid-Autumn Festival is an East Asian harvest festival celebrated notably by the Chinese and Vietnamese^[2][3] people. The festival is held on the 15th day of the 8th month of the lunar calendar with full moon at night, corresponding to late September to early October of the Gregorian calendar with a full moon at night.^[2]

Mooncakes, a rich pastry typically filled with sweet-bean or lotus-seed paste, are traditionally eaten during the festival. By Wikipedia 

Whether you plan to live in Saigon, or anywhere in Vietnam, for one month or more, it is best to be prepared or you'll later get regrets like us.
We started living here almost a year ago for personal reasons. On the first few months of living here, we spent quite a sum of money. We visited restaurants, bought some sweets and snacks for when we are at home, in short, we bought everything we thought was cheap and good. What we didn't know is that it can be cheaper than that.