Body stamp dates were used by Fender from the early 1950's to the mid 1960's and then stopped until the 1980's where they started again sporadically to this day, sometimes you see them and sometimes you don't.Potentiometer codes are pretty reliable for dating, usually indicating the year and week it was made.
Ever since Fender started making basses in 1951 they dated certain parts and components to give a general idea of when the instrument was produced.
So if you have Fender with a neck date of 1964 and the pots are dated 1965, then you have a 1965 Fender Bass.
There are some years in particular that can get real tricky.
The problem is that a neck might be made and dated and then sits in the factory for awhile until it's finally bolted to a body that is dated months later.
Then there are pickup and potentiometer date codes, serial numbers and even bridge stamps and pickguard codes in some cases.
They just grabbed whatever part or component was ready and put together the instrument to fill an order as fast as possible.