How to get the timestamp of last record change?
Such mechanism does not exists in Firebird, so you need to build your own. Add a timestamp column to your table, and create BEFORE INSERT OR UPDATE trigger to write a new value to it. Example:
ALTER TABLE employee ADD last_change timestamp;
SET TERM ^ ;
CREATE TRIGGER EMPLOYEE_BIU0 FOR EMPLOYEE
ACTIVE BEFORE INSERT OR UPDATE POSITION 0
new.last_change = current_timestamp;
SET TERM ; ^
That's all. If you wonder what are those SET TERM statements, there is a FAQ about it.