In early 1904, the Teamsters aligned all their contracts to expire simultaneously on May 1, 1905.

Today will be a "triple witching" day when futures and options on stock indexes and options on stocks expire simultaneously.

The first members appointed to the Board will be divided into three staggered classes in order to ensure that their terms do not expire simultaneously.

But unlike many of the previous sessions in which stock index futures, index options and regular stock options expired simultaneously, most investors went home happy.

Triple-witching days, the Fridays when three sets of options and futures contracts simultaneously expire each quarter, have historically brought wide swings to the market.

This unwinding must be completed by Friday, the so-called triple witching hour, when stock index futures, index options and regular stock options expire simultaneously.

Many traders sold some shares late in the day in anticipation of today's "triple witching," when futures and options on stocks and stock indexes expire simultaneously.

Under old trading rules, all three expired simultaneously on the third Friday of March, June, September and December.

When stock-index futures, index options, and options on individual stocks simultaneously expire, traders feel pressure to use them or lose them.

Yesterday's session was also a "double witching," when options on individual stocks and options on stock indexes expire simultaneously.