How are car model years identified?

This is very much a familiarity thing. In many instances, a car enthusiast will be able to identify a car based on its shape, styling, etc. This is especially prevalent with old American muscle cars.

You can tell the year a car is made from its VIN, vehicle identification numbers were added in the 80s but it's not something you can see from a distance. They'll be linked to the number plate of the car through whichever national agency deals with car registrations, though. This means that in a modern environment, you can use ANPR to detect the plate and bring up the car information on screen, and in a less modern environment you could call it in.

Furthermore, in some countries, the year of registration is detailed in the registration number - for example, in the UK, car registrations follow a AA52 BBB format, which AA is the region the car was registered, 52 indicates it was registered in the second half of 2002, etc...

A lot of the time in movies, it will be "pointing out the classic car make/model", the rest of the time it will be artistic license.

License plates may date a registration but not the car model year.If you actually have custody of the car there is a plaque,in the doorway generally,that gives some detailed information about the car's manufacture (where and when) and specifications as well as the model year.This information would be cross-indexed in government records to the plate and VIN.

Police and similar agencies will include vehicle identification as part of their training. Knowing popular models are crucial in being able to identify suspects on the fly. Most cars go by generations, and years in a generation will use similar if not identical body parts. Toyota for example has the Camry in Generation 4, for 1996-1998, and Gen 4.5 1999 to 2001, very similar, but Gen 3 and Gen 5 are completely unique. Cops will know because they train for it, just like they do many things regular people would not look for (verbal or physical tics, marks, etc).

Some model cars are unique year to year. They simply keep up with most cars. And as 99% of cars will label their make and model on the car, it's easy enough to narrow down.

Obviously naming the car by year is a bit dramatized, but it's not impossible for someone to be able to tell a model year apart.

North American license plate numbers typically have no vehicle-specific information encoded in to them like they do in the UK. In Ontario Canada, for example, when you buy an ordinary new plate, you get what you get "from the bin"; the number itself encodes nothing about the vehicle it will be placed on, the date of purchase, or area in which it was done. The only association between plate number and vehicle is in the records created by the registration. The purchaser owns the plate and can subsequently transfer (re-register) it to another vehicle, so the number itself says absolutely nothing about the vehicle on which it is displayed. Given a plate number, the only information a police officer will have about a vehicle is what comes up on their computer system.

From about the 1950s to perhaps as far as the late 1970s, American manufacturers made fairly noticeable styling changes with each model year (planned obsolescence to some extent). There were generational changes every few years which have been quite obvious, but even within a generation, the yearly styling changes were quite noticeable. From somewhere in the 1970s onward, yearly changes within a generation have become much more subtle, perhaps even disappearing altogether for some makes/models.

So, in older shows where older cars are involved, you may hear specific model years identified, but newer shows involving newer cars will probably be less precise.