Unless the contrary intention appears, a reference in this Act to a period in a year of tax during which a person held a car is a reference to the period that:
(a) commences on whichever of the following times is applicable:
(i) if the person held the car at the time of commencement of the year of tax--that time;
(ii) in any other case--the time in the year of tax when the person commenced to hold the car; and
(b) ends at whichever of the following times is applicable:
(i) if the person continued to hold the car until the time of the end of the year of tax--that time;
(ii) in any other case--the time in the year of tax when the person ceased to hold the car.