I know that this can be seen as something of a pointless issue, as an actual timeline to the MU doesn't mean a lot to some. I remember watching Joe Quesada in person talk about how Franklin Richards was just never going to grow up. But I'd still like to see if there's any sense that can be made of the MU timeline, and see if anyone has any ideas on how much time has passed in the real-world-55 years since FF#1
So here's what I got...
1961 Nov. - Fantastic Four #1 - Johnny is stated to be 16.
1962-1963 - Amazing Fantasy #15 & Amazing Spider-Man #1 - Around this time, Peter is supposed to be 15, which makes him at least 1 year younger than Johnny, depending on how much time passed between these 3 issues.
1963 Sept. - X-Men #1 - Cyclops, Jean Grey, Beast, and Angel are stated to be 18 at this time, while Iceman is 16.
1965 Sept. - Amazing Spider-Man #28 - Peter graduates high school, beginning college 3 issues/months later, in December. So more or less, it seems the comics have been in real time up to now. But Peter stays in college for a long time.
1966 May - Fantastic Four #50 - Johnny Storm begins college. It was previously stated that he had delayed college due to being in the Fantastic Four. If this is still real-time, and he's 1 year older than Peter, that means he put it off for two years, but given how time began to be compressed after Peter started college, it's probably best to state one year, and the 5 months between him and Peter starting could be like a couple weeks.
1968 Nov. - Fantastic Four Annual #6 - Birth of Franklin Richards, and of continuity problems forevermore.
1978 Oct. - Amazing Spider-Man #185 - Peter graduates college, making the past 13 years condensed into 4.
And that's all I got for now. Because I'm not up to date on modern comics, I don't even know how old Franklin Richards is supposed to be. So anything that further gives evidence of concrete amounts of time passing would be awesome.