No, I’m not remembering it wrong. If you google the net, you will find many references to the 1945-1960 dates.
A lot of people and marketers, real estate businesses, sociologists and so on make up their own categories but the government tells us what it is and that is what the national data (like the GAO)is based on.
‘They’ may have told you something or as you implied are still telling you that but it is wrong.