(1) The application of ORS 316.557 to 316.589 to taxable years of less than 12 months shall be in accordance with rules adopted by the Department of Revenue.
(2) In the application of ORS 316.557 to 316.589 to a taxable year beginning on any date other than January 1 there shall be substituted, for the months specified in ORS 316.557 to 316.589, the months which correspond thereto.