Double witching hour refers to the final hour of the stock market trading session where two classes of options or futures expire. The two classes that expire during the double witching hour may be stock options, index options and index futures. The double witching hour occurs on the third Friday of each month, except for March, June, September and December. During the double witching hour, traders often scramble to offset their futures and options positions - meaning that a double witching hour is often a time of volatility. The heavy trading during a double witching hour can cause significant fluctuations in the value of the underlying stocks. A related term, the triple witching hour, is similar to the double witching hour except that three classes expire simultaneously instead of just two.