It's at least 12 years, yeah. It's meant to be 14 years since the Fantastic Four got their powers. Spider-Man and Hulk were next, then the Avengers, Daredevil and X-Men appeared. The first couple of years was real time (leading up to Reed and Sue's marriage and Peter's high school graduation). After that it's roughly four or five real world years to one in-universe. 1963 was 56 years ago. 56/4 = 14.
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