The reason why the Chinese people celebrate the Winter solstice is related to the theory of Yin and Yang. According to the Chinese astrology, Yang symbolizes masculine and positive, Yin has the opposite meanings. The ancient people think from the winter solstice, the Yin is at its peak and will disappear gradually. While the Yang or positive things will become stronger and stronger from the day. So winter solstice is regarded as an auspicious day to celebrate.