UPDATE 2/27/23: Details related to supply-chain issues, as well as specific 2023 and 2024 model-year information, were added to this story.You don’t need to travel at the speed of light to witness time travel. In fact, all you need is a subscription to Car and Driver to see the theory at work. How else can you explain the way we always send you a magazine dated at least one month ahead of the month of receipt?It’s not just magazines that appear to bend the space-time continuum. Vehicle model years frequently differ from the official calendar year. Your calendar may display the year 2023, but somehow new-car dealerships across the country are starting to stock 2024-model cars and trucks. What gives?Blame Franklin D. Roosevelt. Originally, automobile model years tracked calendar years. However, that practice changed in the mid-1930s, after FDR signed an executive order that dictated automakers release their new vehicles in the fall of the preceding calendar year “as a means of facilitating regularization of employment in the [automotive] industry.” Auto assembly-line workers are typically idled during a new-model changeover, and the president reasoned that if their idle period were to happen earlier in the fall, autoworkers would be able to maintain employment through the holiday season and would thus be able to spend more money.Some 90 years later, the tradition of releasing new vehicles in the final months of the preceding calendar year remains common. This custom, however, is by no means set in stone. Under Environmental Protection Agency rules, manufacturers can introduce a next-model-year vehicle for public sale as early as January 2 of the preceding calendar year—for example, a 2024-model-year vehicle can be sold starting on January 2, 2023. Conversely, manufacturers can introduce and release a new vehicle for sale as late as December 31 of the corresponding calendar year, so a 2024-model-year vehicle can be introduced up to and including December 31, 2024. Due to this wide latitude, manufacturers often bring out vehicles well before—and after—the traditional pre-holiday period.Two examples from the recent past are the 2016 Kia Sorento and the 2016 Mazda CX-9. While both vehicles wore the same model-year designation, the two mid-size crossover SUVs were released at very different times. In Kia’s case, the Korean company began selling its new 2016 Sorento in January 2015. At the time, a Kia spokesperson explained: “Model-year designations may be assigned because of the vehicle’s larger life-cycle plan.” The spokesperson added that “marketing, fuel economy, and homologation reasons” are also at play in this decision, and regulatory requirements may change from model year to model year.Meanwhile, Mazda chose to release its then-new 2016 CX-9 in the middle of the 2016 calendar year—nearly a year and a half after its Kia competitor. At the time, a Mazda spokesperson noted to us that several factors went into the company’s decision to label the late-release CX-9 a 2016 model and not a 2017, including Mazda’s desire to avoid potential consumer confusion that can come from selling a next-model-year vehicle in the current calendar year.Like Kia’s spokesperson, though, Mazda’s acknowledged that marketing also played a role in the CX-9’s model-year designation: “Based on [model year] 2016 numbers, the CX-9 [had] the best fuel economy of any non-hybrid mid-size three-row [SUV] in its class.” Had Mazda marketed the CX-9 as a 2017 model-year vehicle, it potentially would have lost that brag-worthy claim. Though the Mazda CX-9 retained its fuel-economy crown among its non-hybrid peers for the 2017 model year, the brand had no way of knowing this at the time of the SUV’s debut.More recently, supply-chain issues—largely related to the COVID-19 pandemic, as well as other factors—have forced automakers to launch new model-year vehicles at earlier and later dates. For instance, Honda started selling the 2022 model-year Odyssey minivan early in the 2021 calendar year as a result of a supplier-related issue.As a spokesperson for the company shared with us at the time: “The timing of model year introductions varies from model to model for a number of reasons, some of which are out of our control. We pulled forward the introduction [of] the model year 2022 Odyssey primarily due to the discontinuation of the HondaVac feature in the Odyssey Elite at the conclusion of the 2021 model year based on a supplier issue.”More on the Sorento and CX-9Denoting a vehicle’s model year is its Vehicle Identification Number or VIN. In the early years, VINs—which were introduced in 1954—lacked any standardization. It wasn’t until 1981 that the National Highway Traffic Safety Administration required all vehicles sold in the United States to adopt today’s 17-character VIN, the tenth of which designates the model year. The letter P indicates the 2023 model year—or the 1993 model year—and R means 2024.Before the ascension of the VIN, manufacturers relied on their own internal serial numbers for marking specific vehicle information. This convention allowed automakers the freedom to determine a vehicle’s model year at will. Case in point: Faced with a backlog of unsold cars in 1951, Kaiser simply added a handful of new trim pieces and changed the serial numbers of leftover 1951 models in order to sell the cars as new ’52s. The company did the same thing two years later, renumbering unsold 1953 cars as 1954 models.Ultimately, the reasons a vehicle’s model year often fails to sync with today’s calendar year are fourfold: historical precedent, regulatory rules, marketing considerations, and, as of late, supply-chain issues. Time travel, however, has nothing to do with it—unless you happened upon a DeLorean in the mid-1950s.This story was originally published on November 11, 2016.Senior EditorDespite their shared last name, Greg Fink is not related to Ed “Big Daddy” Roth’s infamous Rat Fink. Both Finks, however, are known for their love of cars, car culture, and—strangely—monogrammed one-piece bathing suits. Greg’s career in the media industry goes back more than a decade. His previous experience includes stints as an editor at publications such as U.S. News & World Report, The Huffington Post, Motor1.com, and MotorTrend. More