When you trade a stock, there is typically a lag between the day you trade, and the day that the trade is actually finalized or consummated. This lag is usually 3 days.

When it comes to dividend payments, the important date is the list of owners as compiled in the evening of the record date. Those on that list get paid a dividend, those not on it don't. Once the record date is set, the stock exchanges set an ex-dividend date two days prior, and since trades settle in a 3 day cycle, buyers of the stock who buy prior to the ex-dividend date will receive the upcoming dividend, as will any sellers who sell on the ex-dividend date or beyond.

Key point to all of the above is that you can almost forget about all of the record date stuff, the key date for buying/selling is the ex-dividend date, and the term literally means that any buyers are buying the stock without (ex-) the right to the next dividend.


Now, as to the price going up and down, that's another matter altogether. In an entirely rational market, one that perfectly discounts stock valuations, then the price paid on ex-dividend date would have a downward component exactly equal to the amount of the dividend. But the price drop due to the loss of the dividend is only one of the factors that changes a securities price on any given day, and it is entirely possible that the bulk of the price movement, even on an ex-dividend day, is due to other factors such as sector movement, company news, irrational buying/selling by investors, short squeezes and short attacks. And of course, if you don't perhaps believe that the market is a perfect discounting mechanism, then there is even more room for unexplained price behavior.

Key point to that is that while the ex-dividend event has a contribution in the price movement, is it by no means always a dominant one.