In Business, the traing day is the time span that a particular stock exchange is open. For example, the New York Stock Exchange is, as of 2006, open from 09:30AM to 4:00PM. Trading days never take place on weekends. When a trading day ends, all share trading ends and is frozen in time until the next trading day begins. There are several other special circumstances which would lead to a shortened trading day, or no trading day at all, such as on holidays.