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Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.

Model year vs build date

So my "2018" P3D+ has a build date of 12/18, and the corresponding J date code.

My "2023" X was built in 11/22, but has a P date code.

It only matters because of market value, a '19 being worth more than an '18.

Any idea why the X was built a month earlier than the 3 but is a "next year" model? I remember back when I got the 3 that Tesla didn't really do the whole model year thing, IIRC they used to not even list model years on new inventory on the website but I guess that's changed at some point.
Because back in 2018 tesla was not releasing the new model year until the actual year flipped over, unlike every other manufacturer (you mention this already). They switched to releasing new models in the previous year (like every other car manufacturer) in 2019, I think (but am not sure). I am sure they were doing it by 2020, but I think they switched in 2019 physical year, to model year 2020 model 3s being released in october ish.

Nothing any of us who got 2018s can do, really, and the older your car is the less it actually matters on resale.
As noted in the previous post, Tesla started following a more traditional model year schedule in 2019 with cars built in Q4 2019 being sold as 2020 models, cars built in Q4 2020 being sold as 2021 models, etc. Teslas have always had model years, they just had been tied to the calendar year.
Model year N cannot be built before January 1, N-1, nor can it be built after December 31, N. But within that time range, car companies have considerable discretion on when a model year starts and ends. An example would be the skipping of the 1983 model year for Corvettes sold to the public.