It was harder to find the Excel formula for calculating the stock option expiration date than I thought, but here it is:
=EDATE(TODAY(),BM4)-DAY(EDATE(TODAY(),BM4))+8+14-WEEKDAY(EDATE(TODAY(),BM4)-DAY(EDATE(TODAY(),BM4))+2)
The cell BM4 should contain the number of months from today. So BM4=0 returns this month’s expiration date. BM4=1 returns next month’s expiration date. The third Friday of the month is the expiration date for stock options.
Reference: 3rd Friday every month [ExcelBanter]