Famous meteorology expert Feng Peng-nien points out that the ancient Chinese observed sunrise and sunset and they called the time between one sunrise and the next a "sun," which is the Chinese word for day. Then they saw that the shape of the moon changed, and so they called the time between one full moon and the next a "moon" (or month).
著名的氣象專家馮鵬年指出，先民觀察日出日落，將這次太陽從地平面昇起、到下次太陽從地平面昇起之間的時間，稱為一「日」；然後又看到月亮有陰晴圓缺，於是將月亮圓缺一次所需要的時間稱為一「月」。