Summer Solstice & Yin-Yang

Many Westerners have heard of the yin-yang theory, but few know much about it. Even lesser known is that the summer solstice is regarded as the starting point of yin, which is associated with darkness. But the summer solstice is when the longest daylight of the year occurs! How can it be the starting point of the darkness-related yin? The answer is in this brief video...