used to talk about something that happened in the past
One day, I came home to find my windows smashed.
어느 날, 집에 돌아와 창문이 깨져 있는 것을 발견했습니다.
at some time in the future
I'd like to go to Berlin again one day.
언젠가 다시 베를린에 가고 싶습니다.