So many decades

A few days ago, I was just thinking that, pretty soon, I will have seen 8 different decades and yet only still be in my early 60's... Let's check that out. I was born after World War II in the forties, grew up in the fifties, went through the crazy sixties, stabilized in the seventies, raised a family in the eighties and the nineties, discovered retirement in the first decade of the 21st century and am now ready to step into the second one. Recount if you will, that makes 8 of them. Perhaps a mathematician will explain that trick and tell me why I'm still so young. For the moment, as my wife told me the other day, I doubt very much that there will as many decades in store for me...