There is no way to know the actual build date.

So, if those original items are missing from your car, there is no way to know what dates they had.

They could be before, or after the scheduled production date on the fender tag / broadcast sheet. That date is the day they hoped to build the car, but several examples of early / late built cars exist.

If your original Mylar door sticker is still present, it will show the actual build month.