Pre-Open Session vs Special Pre-Open Session in the Stock Market Pre-Open Session vs Special Pre-Open Session in the Stock Market In the stock market, trading happens throughout the day, but not all trades happen during regular hours. Kiran Shroff / Monday, February 24, 2025 / Article rating: 5.0 There are specific sessions, called Pre-Open Sessions and Special Pre-Open Sessions, that occur before the official market hours.