UPDATE ON PASSAGE OF TIME:
So, I've seen that in January of this year, it was revealed that FF (1961) #1 happened 15 years ago, this means that we're in Year 15 in 2025, this creates a bit of a problem with what we were used, as in theory we should be in Year 17 now, with the old method of 4:1. I feel I need to say this, as not only mine, but other timelines like Earth-7642 or the Millarworld on this site used that method to date their events.
It seems that this is no longer the case, so, Marvel didn't specify when a year starts or when it ends, so we need to go with references. And I think Marvel Database (even tho it isn't finished) is the most up to date, so according to their timeline at the moment roughly looks something like this:
Marvel Universe Year One - The Fantastic Four are founded, Ant-Man, Wasp, Spider-Man, Hulk and Thor Starts their careers.
Marvel Universe Year Two - Iron Man and Daredevil starts their Careers; The X-Men and the Avengers are founded, Cap returns, first crossover between JLA and Avengers from Unlimited Access; Man-Thing is born, Deadpool starts his career.
Marvel Universe Year Three - Star-Lord and The Punisher starts their carreers, The Titan Genocide, Gamora is adopted and training, Franklin Richards' birth, Gwen Stacy''s Death.
Marvel Universe Year Four - Moon Knight starts his career.
Marvel Universe Year Five - The First Clone Saga.
Marvel Universe Year Six - Peter Parker graduates from ESU, Ant-Man II starts his career, The Dark Phoenix Saga.
Marvel Universe Year Seven - Luna Maximoff is born,
Marvel Universe Year Eight - Power Pack is founded.
Marvel Universe Year Nine - The Generation X of mutants begins thier education.
Marvel Universe Year Ten - The Second Clone Saga.
Marvel Universe Year Eleven - Valeria Richards is born.
Marvel Universe Year Twelve - nothing important for now.
Marvel Universe Year Thirteen - The Young Avengers are founded, The Genosha Genocide.
Marvel Universe Year Fourteen - Planet Hulk, Civil War.
Marvel Universe Year Fifteen - Secret Wars (2015). And the rest I guess.