" From my own experience, I can't think of an instance where a date of record has been set prior to the announcement of the event, but I certainly haven't heard of every such occasion."
I thought it was common business practice to inform holders of the dividend date in advance.
Example
Urgent Notice to Warrantholders
-- Warrantholders wanting to qualify for the Merrex dividend of 18,675,000
shares of Frontline Gold Corporation MUST have their warrant exercise
COMPLETED by the April 15, 2010 dividend Record Date.
Kerry.