Investopedia explains 'Ex-Date'
This is the date on which the seller, and not the buyer, of a stock will be entitled to a recently announced dividend. The ex-date is usually two business days before the record date. It is indicated in newspaper listings with an x.
Investopedia is a fabulous place to learn a lot about trading terms. Check it out here: http://www.investopedia.com/terms/e/ex-date.asp#axzz2D8318HIB