Nostalgiosity is by definition only experienced by the younger generation. In general, their views are do not represent accurately the times which they are referring to, and often times the things they feel nostalgiostic about are simply wrong. Hence, nostalgiosity is a very generation specific feeling that relates to how the olden times must "appear" to the newer generation. Nostalgiosity about a specific time cannot be felt by the original generation.
"Wow I wish I grew up in the middle ages. Then I would be knight and I would be chivalrous, and I would yearn for my pricness and fight in jousting matches for her. Those must have been heroic times"
"I'm feeling nostalgiostic for the early days of video games. I would have loved to be hacking pong machines, and taming space invaders on the Atari. Or putting together scrap metal to make arcade games. Wow, those were the times."