Generally speaking, an antique is anything that’s at least 100 years old. So that means I'm well on my way to qualifying. Kidding.
This "100-year-old rule" is both the common law definition as well as the definition employed by the U.S. Customs Service. If a piece was made after 1909, it's not an antique—it is, at best, an "antique in the making" (in the case of a fine reproduction). More typically, it's termed a "vintage" piece, a “collectible,” or simply "junk." And there's a lot of that going around these days.