The neck date simply refers to the date that the individual component was produced.
Most notably, production dates have been penciled or stamped on the butt end of the heel of the neck of most guitars and basses.
instrument production history, production dates have been applied to various components.
There were periods of time when this was not consistently done, (between 19), and there are certainly other examples of short periods of time, and individual pieces, where the dating was simply omitted.
While this neck dating is useful in roughly determining the age of a guitar, it is certainly not definitive.
But once again, due to the modular nature of Fender's production methods, and the fact that most serial numbers schemes are not sequential and usually overlap from between 2 to 4 years, (from the early days of Fender, through to the mid 1980s), dating by the serial number is not an exact science.
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.
While there have been periods where dramatic changes have occurred, for example: the transition periods between Leo's Fender and the CBS years, as well as the transition between CBS' Fender and the current ownership, generally speaking, most models are feature specific and do not change from year to year..
Serial numbers have been used in various locations on Fender instruments through the years.