Using the Vin number on the fire wall you can use a Nissan FAST account and pull up all of the information about the chassis and build, including build month and year.
"The importer must file with CBP, upon entry, an EPA form 3520-1 (with a copy of title, etc. attached) and declare code "E" on that form. CBP may waive this requirement for nonresidents traveling temporarily in the U.S. in Mexican or Canadian registered vehicles with no intent to sell the vehicle. You can also obtain the form by calling EPA at 734-214-4100.
The importer is also required to file a DOT form HS-7, which may be available at the port of entry and can be downloaded from the DOT Web site or by calling the Auto Safety Hotline at 1-800-424-9393.
If the car is old enough to be exempt from DOT requirements (the same documents that would confirm this for EPA purposes should also address this issue) the importer may check the block on the HS-7 stating the vehicle does not have to confirm to DOT requirements.
If the vehicle is not old enough to be exempt from DOT requirements, the importer will have to provide proof that the car conforms to DOT safety regulations. Options include a letter from the original manufacturer or a sticker on the inside of the driver's door indicating that the car was manufactured to U.S. standards.
If the importer is unable to prove that a car conforms to DOT requirements, it will have to be imported through a Registered Importer (RI). Classic or antique vehicles are subject to a 2.5% duty rate, which is based on its worth at the time of import. Canadian-made vehicles are generally duty free, provided the importer has valid proof of its origin."
Quote from:
https://help.cbp.gov/app/answers/detail ... to-the-u.s.