What does it mean that there is no shadow for a period of time in the Spring and Autumn Period?

It means that spring and autumn come too fast and go too fast.

The troubles of spring come and go. It seems that people are drunk and it is difficult to wake up. Misty rain is wet and dry. Apricot blossoms shock the cold. Spit and knock on the pot. Never call anyone. I owe you more clothes tonight. Does that man know?

Spring, the first of the four seasons, refers to the period from beginning of spring to long summer, including solar terms such as beginning of spring, rain, fright, vernal equinox, Qingming and Grain Rain. Spring represents warmth and growth. In spring, the qi of yin and yang begins to change, and everything germinates and grows with the rise of yang. As far as solar terms are concerned, spring in China begins in the beginning of spring (February 2-5) and ends in the long summer (May 5-7). In Europe and America, spring begins at the vernal equinox in China and ends at the summer solstice. In Ireland, February to April is designated as spring.