EBay, Collectors, Flea Market & Antiques

The definition of vintage depends somewhat on what kind of item it is.
1. A widely used definition is anything more than 20 years old.
2. A second definition is "anything from 1969 or before." That date doesn't have anything to do with politics, economics, pop culture, how well the item was made, or who made it or where it was manufactured. It's because collecting (whatever you can think of to collect) as a hobby began in earnest in the 1970s, and so stuff in its original unopened unused condition from the 1960s and before is much harder to find.
3. A third possibility is "when the item was in its heyday" or when it was first manufactured. Some examples: Barbies 1959-1972 (when the items were made in Japan), Star Wars 1977-1983 (the release dates of the original three movies), Star Trek 1966-1969 (when it originally aired). Keep in mind that many items have been in continuous production since they were first introduced, and many items have been reproduced in the past 20 years; for example, Fiesta Ware, LPs, furniture styles.