The ex-dividend date is two business days prior to the record date. To be a stockholder on the record date an investor must purchase the stock before the ex-dividend date. The latest date he can buy the stock to be a stockholder on record and be entitled to the dividend would be one day prior to the ex-dividend date (this includes extended hours (pre-market and after-hours) of that day) to allow for the three stock trading day settlement of the stock purchase. If the investor purchases the stock the day before the ex-dividend date the investor would be a stockholder on the record date and would be entitled to receive the dividend payment.
Ex-Dividend means the stock trades Ex (without) the dividend on that day.
The share price on Ex-Div day will be reduced by the amount of the dividend as that $ is put into an account to be paid out on the Pay Date.