在潮差逐日变化的半个朔望月的周期里，有朔望大潮，它与月相有关。

In the tidal difference daily variations, there is a period of half lunar month of syzygy spring tides related to the phase of the moon.

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沙罗周期日数约为朔望月周期（29.53 日）、 交点月周期（27.21 日） 和近点月周期（27.55 日） 的最小公倍数。

It is approximately the LCM (lowest common multiple) of the synodic period (29.53 days), draconic period (27.21 days), and the anomalistic period (27.55 days) of the Moon.

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