Calendars that are based on the moon's orbit around the Earth are known as lunar calendars (Yinli in Chinese), and Solar calendars (Yangli in Chinese) are another category of calendars that are based on the positions of the Sun through the seasons.
The Agricultural Calendar is an integrated lunar-solar calendar as it embraces the movement of the moon as well as that of the Sun. In ancient time, observation of moon phases is a convenient way to count the days. For example, new moon goes to first quarter and then to the full moon and last quarter, next it returns to the new moon. Months in the Agricultural Calendar start with a new moon, which occurs when the moon and the Sun move to the same longitude on the ecliptic.
