With Shop Uploader all you need to enter for year_made is the year the product was made. If you don't know the exact year you can enter the first year of the decade
Let us look at a product made in the 1980s.
Etsy's category is 1980s. However, with Shop Uploader you can enter any year between 1980 and 1989 to fall into the 1980s category.
So if your product was made in 1985 you will put 1985 in the year_made column, not 1980s.
For more information on year_made errors visit the error validating year_made articles or the documentation page.