The summer solstice is the point at which daylight is the longest and night is the shortest, and from the Chinese perspective this indicates that the potency of the sun is at its height. From now on it will begin to diminish; the Yang will lessen and the Yin will increase.
在中國人的觀念裡，夏至這一天，晝最長、夜最短，表示陽氣到了極致，接著就要走下坡，開始陽消陰長了。