noun, adverb
same day; on the day
Used adverbially or as a noun to indicate that something happens or is done on the same day, often in formal, business, or news contexts.
即日発送いたします。
We will ship it the same day.
面接の結果は即日通知された。
The interview result was announced on the same day.
当日 means 'that day' or 'the day in question', often referring to a scheduled event day, while 即日 emphasizes immediacy and same-day action.
同日 also means 'the same day', but is more neutral and often used in comparisons or references to a previously mentioned date, whereas 即日 carries a nuance of promptness.
Compound of 即 (immediate) and 日 (day), literally 'immediate day'.