Regular Trading Hours (RTH) are the standard trading hours for a specific financial market or exchange during which trading can take place.
RTH are typically set by the exchange or regulatory body that oversees the market and are the hours when the majority of traders are actively buying and selling securities on the exchange. For example, the New York Stock Exchange (NYSE) operates Monday through Friday from 9:30 a.m. to 4:00 p.m. Eastern Time, which is considered RTH for that exchange.
Trading activity may continue outside of regular trading hours via electronic communication networks (ECNs) or other alternative trading platforms, but with fewer participants and potentially higher volatility due to lower liquidity.
Also see ETH