On March 21, 2025, a substantial $4.7 trillion worth of options are set to expire in the U.S. stock market, marking a significant event known as 'quad witching day.' This day, which occurs on the third Friday of March, June, September, and December, involves the simultaneous expiration of index futures, index options, and stock options. Among the expiring options, $2.8 trillion pertains to S&P 500 index options, while $645 billion is associated with single stock options. Traders are advised to prepare for increased volatility and trading volume, particularly during the 'witching hour' from 3 PM to 4 PM EST, as funds rebalance their positions. This expiration event is noted as the largest since December 20, 2024, and the majority of the options expiring today are puts, necessitating traders to decide whether to exercise, roll over, or close their positions.