A more thorough explanation:

Definition: The ex-date, also known as the ex-dividend date, is the date on or after which the buyer of a security does not acquire the right to receive a recently declared dividend.

For example, if a company declares a dividend of $0.50 per share and the ex-date is set for June 1st, then anyone who buys the stock on or after June 1st will not receive the dividend. Only those who owned the stock before the ex-date will receive the dividend.

This is important for investors to keep in mind when buying and selling stocks, as the ex-date can affect the value of the stock. If an investor wants to receive the dividend, they must purchase the stock before the ex-date.