There is no firm rule here, but the term “vintage” generally refers to a period starting at least 20 years ago. I find that most collectors, when using the term “vintage”, are referring to watches made in the 1980s or earlier. I personally use the term to refer to pieces from the mid-1970s and earlier.
Some people use the word “antique” in reference to timepieces, most often in describing pieces from the 1920s and earlier. Personally, I lump those together under a broad classification as “vintage”.