는 데 걸리다

how long something takes

"-는 데" here means "in doing it" and 걸리다 is "take (time)". Nearly every line is the fixed phrase 걸리는 시간, how long something takes: how long it takes to steep, how long it takes to make this, how long it took to become a super-aged society, the time it takes the Earth to go once round the Sun. Note one line uses a different 걸리다 — 이게 하나밖에 없는데 걸린다고 is "get caught", the same spelling with an unrelated meaning.