Quadruple Witching
The quadruple witching hour is the last sixty minutes of the trading day on the third Friday of March, June, September, and December, when contracts for stock index futures, stock index options, stock options, and single stock futures expire simultaneously
Quadruple witching always amps up the volatility - I've seen wild swings in those final hours as positions unwind. Classic reminder to manage risk heading into expirations
I had never realized that was even a thing!