18.—(1) The Department may by order subject to negative resolution substitute a new date for a date for the time being specified in section 9, 10 or 11.
(2) An order under subsection (1)—
(a)may specify a new date for all purposes or for specified purposes only,
(b)may specify different dates for different purposes.
(3) Before making an order under subsection (1) the Department shall consult the Comptroller and Auditor General.