Nostalgia isn't delineated by a specific length of time, it is a fondness or longing for something that is past, that no longer exists or happens, whether a year, a decade or a century ago.
Surely it must relate to one’s personal experiences and memories?
I certainly feel a nostalgia for visits that I made to the USA in the 1960s, but can’t say the same about the 1950s, much as I might think I would have enjoyed it then.