Audio Guide：

It takes about 24 hours to complete one rotation for the Earth. When turned towards the Sun, the bright side of the Earth experiences the day. The same side will then rotate to face the dark and enter night time. Earth also orbits around the Sun. Earth’s spin axis is tilted 23.5 degrees with respect to the ecliptic. This tilt results in the changes of four seasons. Following the workings of nature, humans have devised calendars in accordance with the cyclical phases of the Sun and Moon relative to Earth’s motions. There are three main types of calendars. The solar calendar is based on the positions of the Sun whereas the lunar calendar is premised upon lunar phases. There is also the lunisolar calendar, a calendar that incorporates both the moon phase and the time of the solar year. The traditional Chinese calendar is a calendar of both “yin and yang”; in other words, a lunisolar calendar. The lunisolar calendar defines 24 solar terms based on the weather pattern of each term.