What are the three periods of Qingming in ancient China?

In ancient China, Tomb-Sweeping Day was divided into three stages: "The first stage was when tung trees began to blossom; Second, the vole becomes a quail. "Wait until the rainbow appears. "

That is to say, at this time, the white paulownia blooms first, then the happy voles in the shade disappear and all return to the underground caves, and then the rainbow can be seen in the sky after the rain.