I was up at the crack of down.
→  새벽에 일어났어.

[예문]

A: You look like deayh  warmed over. Are you sick?
   너 오늘 너무 안색이 안 좋아 보인다. 어디아파?

B: no. I was up at the crack of dawn today.
  아니야. 오늘 새벽에 일어나서 그래.

A: It is Sunday. Why did not you sleep in?
   일요일이잖아. 좀 더 안 자고?

B: I wanted to, but the neighbor is dog would not stop yapping.
   그러고 싶었지만 옆집 개가 계속 짖어댔거든.