"Quadruple witching" refers to the simultaneous expiration four times a year of stock options, index futures, and index futures options derivatives contracts. The fourth type of contract involved in quadruple witching, single-stock futures, hasn't traded in the U.S. since 2020 and was never a major contributor to equity trading volumes. What is now effectively "triple witching" occurs on the third Friday of March, June, September, and December. Equity trading volume tends to rise on these days and is typically heaviest during the last hour of trading as traders adjust their portfolios.