Yin and Yang are cold and hot; soft and hard; wet and dry. Too hot or too cold are not comfortable to human. If a person was born in the hot summer daytime, then the person's internal body is too hot and dry. The person will have better health, better mood, better energy and better luck during the winter time. This is the Yin Yang Balance theory for Chinese astrology.
Yin and Yang are everywhere from sky download to the ground. All animal have female and male. Plants have small and tall. Sky has moon and sun. Time has night and day. Weather has winter and summer. The seasons between winter and summer are names spring and fall.