Can a moon cycle accelerate periodically?

I've been looking for information on this, but I haven't come upon an answer that could actually help me figure this out:

Imagine a planet, inhabited by somewhat "human" beings, that has one sun-like star (a source of light and such) and two moons. Now, that "Sun" and one of the moons work in cycles kind of similar to ours, that being 15 hours of sunlight and 15 hours of night, during which, this moon appears in a roughly opposite cycle to that star.

Now, the second moon has played a crucial part in the disappearing of an ancient city, that being either floods or drought. It may not be directly related, but those living, sentient beings think there is a direct relation between that. The idea is that this moon used to appear during the night for centuries, only to keep changing its span and coming out slightly earlier everyday. The difference of the time it came out from day to day was so small it couldn't be noticed until it started appearing at, what we could call, midnight.

To keep it simple: this moon kept appearing earlier and earlier, and by the time it first came out at the same time their "Sun" did, a natural disaster came to that city.

This happened nearly 1000 years ago, and the theory states that "Every thousand years, this moon switches between day and night". Some of the people who got to abandon the city on time think they can still come back to it, because (they assure), since so many years have passed, the moon comes out at night again, and so, the place must be habitable again.

I'm terribly sorry if this makes no scientific sense at all, my knowledge on physics, planetology and English are quite not as good as I wish they were.

posted over 7 years ago

Elsie‭

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