Past : ㄴ(n), 은(eun)
Present : 는(neun)
Future : ㄹ(l), 을(eul)


For example,

Foods that have eaten
먹은 음식
meogeun eumsik

Foods that are eating
먹는 음식
meokneun eumsik

Foods that will be eaten
먹을 음식
meogeil eumsik


The school that you've gone to
네가 간 학교
nega gan hakyo

The school that you are going to
네가 가는 학교
nega ganeun hakyo

The school that you will go to
네가 갈 학교
nega gal hakyo