SPX and VIX index options trade from 09:30 EST to 16:15 EST, but also during extended hours (overnight) from 20:15 EST to 9:15 EST.
Settlement
Options settle T+1 and a trade on Monday would settle end of day Tuesday. If a SPX or VIX option is traded Monday night after 20:15 EST during the overnight session it will settle Wednesday because after 20:15 EST starts Tuesday’s trading session. Trade Settlement Dates are listed in the Trade Confirmation Report.
PDT Day Trades
The next day’s trading session starts at 20:15 EST so if you Buy to open a SPX or VIX option at 23:00 EST Monday and Sell that same SPX option to close at 10:00 EST on Tuesday morning then that counts as a Day Trade because it is in the same trading session as designate by the CBOE.
Note
- For trading sessions starting on days the NYSE is closed per the NYSE holiday schedule, the Alternative Trading System (ATS) accepts orders from 5:30 PM ET and effects transactions from 6:00 PM ET until 3:50 AM ET the following morning.