What festival was the day before in beginning of spring?

What was the day before beginning of spring? Explain as follows.

"The day before beginning of spring was called Jueri. According to the theory of Yin-Yang and Five Elements, after beginning of spring, the wood was flourishing and the water was extinct. After the long summer, the fire is flourishing and the wood is absolutely dead; After beginning of autumn, Jin Wang caught fire; After the beginning of the dead of winter, gold will be lost, so the day before beginning of spring, Changxia, beginning of autumn and beginning of winter is called "Lost Day". What was the name of spring the day before? The day before beginning of spring is called "four days", which refers to the day before beginning of spring, Changchun, beginning of autumn and beginning of winter. In addition to the four musts, there are four separations. These four departures refer to the day before the vernal equinox, autumnal equinox, summer solstice and winter solstice. The day before beginning of spring was the last day when the 24 solar terms ended, and it was also the day when winter and spring alternated. At the same time, a new 24 solar terms will be ushered in. Decisive day is the saying that solar terms alternate in China's lunar calendar.