其规律性的月相使之成为一种非常方便的计时器，很多古老日历的发明都源自对月圆月缺变化的观察。

Its regular phases make the moon a very convenient timepiece, and the periods of its waxing and waning form the basis of many of the oldest calendars.

youdao

其规律性的月相使之成为一种非常方便的计时器，很多古老日历的发明都源自对月圆月缺变化的观察。

Its regular phases make the moon a very convenient timepiece, and the periods of its waxing and waning form the basis of many of the oldest calendars.

youdao