As mentioned above, the regular trading days closes at 4 p.m. Eastern time. However, on early-closure days, which are typically right before or right after a market holiday, the markets will close early, usually at 1 p.m. EST.
There are also ‘after-hours sessions’, which typically span from 4 p.m to 8 p.m Eastern time. It’s worth mentioning that these trades taking place outside regular hours are made over electronic communication networks (ECNs), which allow buyers and sellers to connect directly rather than via a middle person. While this type of trading was previously only accessible by large institutional players, there are increasingly more brokers such as Interactive Brokers and Fidelity which can facilitate this type of trading today.