Unless it痴 a totally new series, tractor and construction equipment manufacturers generally make running changes, rather than model year changes. In many, but not all cases, the running changes will coincide with holiday shutdown periods around Christmas or mid summer.
The tractor will have a tag with date of manufacture, along with the serial number, but that date doesn稚 tie into a particular model year in a legal sense.
Heavy trucks and other titled vehicles are a little different, but even there, model years don稚 necessarily coincide with calendar dates. Heavy trucks, for example, could have a given model year but an engine certified to an earlier standard if the engine was built in the prior year, to the old standards.
I am looking at possibly buying a used CTL. I asked the dealer what model year it was. He replied, as well he should, by giving me the equipment model and build date, with no reference to model year, since there isn稚 one.
Addendum: I happen to have the Deere CTL sales brochure that another dealer sent me sitting next to me. There is no mention of model year anywhere in the catalog. Just a Litho 18-04 (publication / revision date) for a current model CTL.