6. Time past cannot be called back again.

　　光阴一去不复返。/时间不能倒流。

　　相关例句：

　　1. All time is no time when it is past.

　　光阴一去不复返.

　　2. No moment will ever repeat. Savor time with family and friends.

　　光阴一去不复返,要享受和家人朋友共聚的时光.

　　3. No hand can make the clock strike for me the hours that are passed.

　　光阴如流水,一去不回头。