ago/before
전에

~ 과거에 했던 일에 대해 말하려면

a year before, I went to

... ❌
a year ago, I went to... 👍

one hour before, I had to... ❌
one hour ago, I had to... 👍

six months before, I came back from... ❌
six months ago, I came back from... 👍

~ before의 한 가지 중요한 사용할 경우는 perfect aspect으로 된 절에서 더 먼 과거에 했던 일에 대해 말하려고 하는 경우입니다

예를 들어:

one year ago I went to America, and one year before that I had gone to Korea.

I had just gotten home an hour before, when I accidently fell asleep.

~~~in/after~~~
https://hellotalk.com/m/MQOlVKyLzIMTZD==?id=EKNJRN==