The term “Electronic Trading Hours” and “Extended Trading Hours” (ETH) refers to the extended trading periods that take place outside of Regular Trading Hours (RTH) and during which trading in financial instruments can be conducted electronically, frequently using electronic communication networks (ECNs) or other alternative trading platforms.
ETH might vary based on the broker or trading platform being utilized, unlike RTH, which are usually decided by the exchange or regulatory agency. To trade stocks, futures, options, and other securities outside of the exchange's RTH, for instance, certain brokers may provide ETH.
ETH may give traders more freedom to transact outside of standard RTH, perhaps enabling them to profit from breaking news or other market-moving events that take place outside of usual business hours. Yet, due to its lesser liquidity and potentially greater price range, ETH can also be more volatile than RTH.
Also see RTH