Mid Autumn festival, Moon Festival, Festival moon cakes, or the August Moon Festival - they are the different names of the same festival, the Mid - Autumn Festival. It is a popular celebration of abundance and togetherness. The Chinese believe in praying to the moon god for protection, family unity, and good fortune. It falls on the 15th day of the 8th lunar month, a date that parallels the Autumn Equinox of the solar calendar.On this day the moon is unusually bright, clear and round. Historical accounts are silent about the exact origin of this festival, but as far as the assumption of the scholars are concerned, it is related to the two customs in China.
The first customs concern the Chinese farmers. China is an agricultural country and farming in China is intricately associated with the seasons. In the ancient times, the farmers used to worship Earth God and prayed for a good harvest when they sowed the seeds during spring. Once again during autumn, the farmers worshipped the Earth God and offered their gratitude on having reaped a good harvest. This was known as the autumn reward. Some people believed that the
Mid -Autumn Festival orginated from the autumn reward ritual.
The second custom is related to the worship of the moon. The Mid Autumn Festival occurs at the autumn equinox when the sun shines vertically on the equator, equally dividing the day and the night in the northern and the southern hemisphere. At this time, the sunlight shines vertically on the equator, equally dividing the day and night in both the southern and northern hemispheres. In the evening the moon appears with gentle winds and the sky is clear, apart from the light clouds. This is the perfect time to watch the moon. This day was later assigned to the worship of the moon.
This custom of worshipping the moon,called xi yue in Chinese, can be traced back to the ancient Xia and Shang Dynasties (2000 BCE-1066 BCE). In the Zhou Dynasty too (1066 BCE-221 BCE), the people celebrated the Mid-Autumn Festival to worship the moon. This practice became very prevalent during the time of the Tang Dynasty (618-907 CE) and people enjoyed and worshipped the full moon. In the Southern Song Dynasty (1127-1279), people started making round mooncake, as gifts to their relatives as an expression of their best wishes for a family reunion. At night, they came out to watch the full moon to celebrate the festival. Since the Ming (1368-1644), and Qing Dynasties (1644-1911), the custom of Mid-Autumn Festival celebration has become extremely popular and is being grandly celebrated.
The Mid-Autumn Festival is one of the two most important holidays in the Chinese calendar, the other being the Chinese Lunar New Year, and is a legal holiday in several countries.
Source : http://www.theholidayspot.com/mid_autumn/origin.htm