During the Northern Song Dynasty (960-1127), the 15th day of the eighth lunar month was designated as the Mid-Autumn Festival. During the Zhou Dynasty (c. 11th century – 256 BC), the night of the roundest moon of the year was an occasion for the Chinese to hold rituals to greet the cool weather and sacrifice to the Moon Goddess. By the Tang Dynasty ( AD 618 – 907) merry-making had become part of the festival, as had watching the moon rise and enjoying its full, silvery light.
When did this festival first begin? No exact date can be found in historical documents, but scholars assume that it is related to 2 customs in China.
The first custom concerns farmers. China is an agricultural country, and farming is closely related to the seasons. In ancient times, farmers worshipped the Earth God to pray for a good harvest, when they sowed the seeds in spring. This was known as spring worship. During autumn, farmers also worshipped the Earth God to thank him for giving them a good harvest. This was known as autumn reward. Since the 15′" month of the 8th month is the time when rice paddies are harvested, some people believe that the Mid Autumn Festival came from the autumn reward ritual.
The second custom concerns worship of the moon. According to astronomy, the Mid Autumn Festival occurs at the autumn equinox. At this time, the sunlight shines vertically on the equator, equally dividing the day and night in both the southern and northern hemispheres. The moon appears in the evening with gentle winds and light clouds. This is the best time to watch the moon. People later made this day, the day to worship the moon.