There are two main seasons in the Skagit Valley, November to early April when the swans are here, and April through October when the swans are not here. Those are the big seasons. Life yins and yangs with the appearance, disappearance of the swans. When the swans are here, is it a yin or a yang? Yin-陰 is shadow or dark, and yang-陽 is light or sunshine. So I suppose when the swans are here, it must be yin considering how dark that time of year is.
In Japanese, the characters are still 陰陽, but in China they have been simplified to 阴阳, and the simplification is rather ingenious, as the right portion of the character for yin is the moon-月, and for yang it is the sun-日.
Another important season are the months when peonies bloom. They opened a few days ago. Peony time is definitely a yang time of year.
