Fashionave.info website uses box dates, that is the year on the box is the year they are listed under, *not* the year they are first listed in Mattel’s Vendor catalog and the year they are first sold.
This website has been around for years. The owner has closed the site and opened a new one. You can find it here on the fandom.wiki site.
I started my own version of a guide to Fashion Avenue with high resolution images sorted by the year the fashions were first pictured in Mattel Catalogs and sold in stores, and by the type like Party, Deluxe or Denim. You can read more about my own Fashion Avenue guide here.