Australian Capital Territory Numbered Acts Australian Capital Territory Numbered Acts4. In this Part—“amended Building Act” means the Building Act as amended by this Act; “Building Act” means the Building Act 1972; “commencement day” means the day on which this Part commences; “specialised system” means a specialised system within the meaning of the unamended Building Act; “unamended Building Act” means the Building Act as in force from time to time before the commencement day.