With a history that spans decades of intricate storylines and elaborate retcons, Marvel's timeline is one of the most detailed fictional chronologies out there.
And this is only made yet more intricate when you remember just how many comics have made huge changes in Marvel's history. Indeed, the past two decades have brought some of the House of Idea's most revolutionary alterations to the universe, both in creating new developments, and retroactively changing how we perceive older events.
While they're not always beloved changes - for example, you see very few people fondly remembering the 'One Day More' Spider-Man storyline - it's these weird and wonderful events that serve to keep comics an interesting and constantly evolving medium. With series like House of M affecting the Marvel universe over a decade after it took place, it's safe to say that these kinds of events are the backbone of the imaginary world we know and love.
Ranging from changing the entire universe in one issue, to changing one character in an unforgettable way, comics that alter Marvel's history are all similar in at least one sense: they're never dull.