at the crack of dawn

• 黎明时分，破晓时分

at the crack of dawn的用法和样例：

例句

1. The marchers jumped off at the crack of dawn.
   行军队伍在破晓时出发了。
2. I was up at the crack of dawn to get the plane.
   为了乘飞机，我破晓时就起身了。