Vehicle year model

I bought a car which was regarded as 2018 model llate ast year, 2018. When I took it for first service to another branch I was told that it wasnt 2018 as per service history. I was told the car was on the floor since 2016. Now I am not sure if I am driving 2018 model or 2016. I went to the dealer to find out. I was told that models are determined by the year in which the vehicle is first registered. I am not convinced with the answer. I saw vehicles been advertised as 2019 models even before they were registered. Please advice.