Non-primary or “electronic” trading hours have two major differences

[Tobi]

Non-primary or “electronic” trading hours have two major differences to the main session for an instrument. The first is that because a futures product is a contract traded on an underlying market (for example a stock index future on a basket of stocks), any trading going on in the future when the underlying market is not fully open is going to be a proxy to the real market. In other words, the trading that goes on in futures outside of primary hours, isn’t always going to be an accurate reflection of what the underlying market wants to do.