What is Tomorrow ?
Tomorrow is (adv) referring to the day after today Are you free for lunch tomorrow? I mustn’t forget I have a dentist’s appointment tomorrow morning. We are going to an Italian restaurant tomorrow evening. (noun) the day after today Today’s Monday, so tomorrow must be Tuesday. Tomorrow is our tenth wedding anniversary. the day after tomorrow two days after today We’re going to Paris the day after tomorrow.
source: Easier English, Student Dictionary Upper Intermediate Level