After Hours (AH) or Overnight Session (ON)

AH stands for after After Hours and refers to the trading session when the cash market is closed but the futures market is open. This is also know as the Overnight Session.

In the electronic markets such as the E-mini S&P500 Index Future there are generally two sessions. The most liquid and most traded session is the RTH session. This usually runs from 9:30am to 4:15pm East coast time. The market is then closed for a brief period from 4:15pm to about 5pm (depending on market) and from when it reopens until the following mornings official open at 9:30am this is called the After Hours (AH) or Overnight Session.

Most institutional traders will only trade the RTH session but will regularly leave stops in place overnight. Small investors and individuals are more common in the overnight session. This is when you are most likely to the stops being run.

This trading session is also referred to as Electronic Trading Hours (ETH).