today and tomorrow
Refers to the two specific days: today and the following day. Often used when discussing immediate plans or deadlines.
Please give me an answer within today or tomorrow.
today or tomorrow; in a day or two; very soon
Used to express that something will happen imminently, within the next couple of days. The exact day is not specified, but the timeframe is very short.
It might start raining any day now.
It seems he's moving out very soon, maybe today or tomorrow.
Compound of 今日 (きょう, 'today') and 明日 (あす, 'tomorrow'). The reading あす is a slightly older or more formal variant of あした, but is preserved in this fixed expression.