시간에: Saying When, and the Words That Refuse 에

The particle that marks places also marks moments. It is the same 에 as in (장소)에, doing the same job in a different dimension: Korean treats a point in time much as it treats a point in space.

The basic use

• 세 시에 만나요 — Let’s meet at three.
• 월요일에 가요 — I’m going on Monday.
• 3월에 시작해요 — It starts in March.
• 주말에 뭐 해요? — What are you doing at the weekend?

English needs at, on and in depending on the unit. Korean uses 에 for all of them, which is one of the rare places where Korean is simpler.

The list that refuses it

This is where learners slip.

내일에 가요.   ❌
내일 가요.     ✅

These take no particle at all:

They are already adverbs — they carry “when” inside themselves, so there is nothing for 에 to add.

Everything else does take it: 월요일에, 3시에, 작년에, 방학에.

There is no rule to derive here. The list is short, and it is worth reading twice now rather than being corrected on it for a year.

Stacking time units

When two time expressions sit together, 에 goes only on the last one:

월요일 세 시에 만나요.     ✅
월요일에 세 시에 만나요.   △  (grammatical, but laboured)

The same applies to longer chains — 다음 주 월요일 오후 세 시에. One 에, at the end.

Telling the time

Korean clock times mix both number systems, and it is fixed:

Hours → native Korean numbers: 한 시, 두 시, 세 시, 네 시
Minutes → Sino-Korean numbers: 십 분, 이십 분, 삼십 분

세 시 삼십 분     3:30
일곱 시 십오 분   7:15

Note 세 시, not 삼 시. Getting this backwards is instantly noticeable, and there is no pattern to reason from — the convention simply is what it is.

반 (“half”) is common for :30 — 세 시 반 is more natural in speech than 세 시 삼십 분.

에 or 부터

3시에 시작해요 — It starts at three. (a point)
3시부터 해요 — We do it from three. (onward)

에 marks a single moment. 부터 marks a beginning that continues. If the sentence has an end point too, you will usually want 부터 … 까지.

Asking when

언제 가요? — When are you going?
몇 시에 만나요? — What time shall we meet?

언제 takes nothing. 몇 시 takes 에, because it is a specific clock time. Both are worth having ready — they are among the first questions you will actually need.