I am afraid that you are wrong.
If invoice/manufacturing date will be 2015 then whether it would be delivered in january or registered in january still it will be 2015 model and this will be also written in registration book that it is 2015 model registered in january 2016
Model year is having worth on selling a car. People on buying consider model year, if it would be Dec 2013 model then it would be having less worth then January 2014 model, just only a difference of 30 days and you will get a loss on ONE year model.