This is a solar calendar system. According to the position of the Sun on the ecliptic, a tropical year (the time the Earth takes for one revolution around the Sun) is divided into twelve parts, which are known as the twelve solar months, numbered with the twelve Earthly Branches🪐. Each month is divided into two halves, the first named “Jie” (season) and the second named “Qi” (climate), totalling 24 periods, which are named according to the patterns in weather and natural phenomena that the ancient Chinese had drawn from their farming experience, and are now collectively named “the solar terms”.