Holden does class cars built after 1st September each year as the following years model.
But people are never going to understand that if the tag says it's 9/77 or 10/77 etc it's a 1978 car, to them it's always going to be a 1977 model.

My VY is an October 2002 but the computer (Tech 2) regards the car as a 2003 simply because it was built after September 1st.