This is the day a buyer of a stock becomes the registered owner; also called the Owner of Record.
The buyer of a stock must be on the company's books as the Owner of Record to receive a normal dividend. Because of the T 2 settlement rule, stock trades must be settled in two business days, meaning that to be an Owner of Record, a buyer of the stock must buy the stock two business days before the record date.
For example, the payment of a corporate liquidation is a distribution, not a dividend, because it represents the proceeds of the sale of the company, not corporate profits.
However, because dividends and distributions are subject to the same date rules by the stock exchanges, for the purposes of this discussion, dividend and distribution shall be synonymous.
The press release will typically include the declaration date, the record date, and the payment date.