This sentence comes from Zhuangzi's Happy Travel. The original text is: "If the sun, the moon and the stars are all time, they are only called eternity." It means that the sun, the moon and the stars all run regularly, and their appearance and disappearance are limited by time. And "flying flowers will eventually have a moon" describes that petals will dance with the movement of the moon and eventually disappear.
This sentence can be used to show that life is short and time is limited, and people must pursue their dreams and goals as much as possible in their lives. At the same time, it also emphasizes the importance of cherishing time and beautiful moments.