At any one time, a basic option has contracts with three expiration dates outstanding. For example, in mid-February, options trading on cycle 3 will have March, June and September expiries available. Late in March, after the March options expire, a December contract will be added, thus offering June, September and December expiries.
Higher-volume equity options, index options, and LEAPS can trade on other cycles, such as Cycle 4, Cycle 5 or Cycle 6. Cycle 4, for example, offers options in the two nearest months plus two months from Cycle 3. For example, in mid-April, there would be April, May, June and September expires available. A month later, there would be May, June, September and December expiries available for trading.
Equity and index options expire on a predictable four-month schedule, two of which are determined by the expiration cycle to which the underlying instrument has been randomly assigned and two by when you purchase the option.
There are three expiration cycles, one beginning in January, one in February, and one in March. Each cycle includes four months, and an option always expires in two of those months. The other two expiration months are the month in which it is purchased and the following month.
For example, if you purchase an option on an equity assigned to Cycle 1, which includes January, April, July, and October, between January 1 and the third Friday in January you have a choice of contracts expiring in January and in February -- because they are the current month and the following one -- or in April or July -- because they are the next two months in Cycle 1.
Similarly, if you purchased an option on the same equity in April, you'd also have a choice of four expiration dates: April and May -- the current and following months -- and then July and October, the next two months in Cycle 1.