Welcome!
I don't know if this is universally true, but my G is considered a '67 model even though it was manufactured in '66 as evidenced by its serial number. Cessna apparently used the same scheme for naming model years as the car manufacturers.
Roy
Roy,
Yes, Cessna did like the auto manufactures. In September of each year they would start the "next" years model line.
Example: In September of 1975 was the start of the 1976 model year planes.
Even shared some of the names with the cars, Citation, Skylark, Skyhawk.