The corporate action announcement date, also called the declaration date for dividends, is the day on which an issuer makes a corporate action announcement to the market. It is the first in the sequence of dates that define an event. Those that follow include the ex-date, from which the security trades without the entitlement; the record date, on which holdings are fixed for entitlement purposes; the election deadline for events with options; and the payment date, when cash or securities are distributed.
The date matters for several reasons. Exchange rules and market standards require a minimum interval between announcement and the dates that follow, so that intermediaries can notify holders and trades can settle. A declared dividend becomes a liability of the company from this date. Some events also have a separate effective date.