at
에 is also added to nouns that indicate time and expresses the time when some action, event, or situation occurs. It corresponds to 'at' or 'on' in English. 에 can also combine with the particles 는 and 도 to form 에는 and 에도.
Of the nouns that indicate time, 에 cannot be added to 그제 (= 그저께) (the day before yesterday), 어제 (= 어저께) (yesterday), 오늘 (today), 내일 (tomorrow), 모레 (the day after tomorrow), or 언제 (when).
When more than one noun representing time is used in a sentence, then 에 is added to the final noun only.
Indicates the time of the action. Can be used with days, hours, seasons, etc.