The numbers and decals are produced far in advance, and apparently, some N9 decals, (which were supposed to be used in 1999), were affixed to some instruments in 1990.
As a result, you will see some 1990 guitars bearing N9 serial numbers.
The following chart details the Fender serial number schemes used from 1950 to 1964.
You will notice that there is quite a bit of overlap of numbers and years.
The American Deluxe Series instruments use the same dating convention but with the addition of a "D" in front of the "Z", i.e. Once again, and as always, there is typically some overlap and carryover of number prefixes from year to year.
The following serial numbers are somewhat outside the more, well known Fender serial number schemes.
If you have what you consider to be a somewhat "odd" serial number, please check the following chart to see if you find your serial number configuration here.
This chart contains With the year 2000 came the introduction of the "Z" prefix serial numbers on US made instruments, which stood for the 0 of the new millennium.
Most notably, production dates have been penciled or stamped on the butt end of the heel of the neck of most guitars and basses.
This chart contains If you are unable to place the approximate year of manufacture of your instrument using the above charts, there are a few great books available, which have invaluable information on the history of Fender instruments.
If you have serious interest in learning about the history of Fender instruments, or if you just want to try to establish the year of production of your own axe, we would highly recommend that you pick up one or more of the following books.
So, obviously a neck date, while being helpful in providing a date range of production, it cannot be a definitive reference.
Unlike the auto industry which has specific model years for their products, most specifications for a given Fender instrument model, change little if any, through the lifetime of the model.