Marvel 1964: Time Travel

 It took this long for time travel to get complicated

Kang is introduced and almost instantly revealed to be the same as Rama Tut. Immortus is introduced but gets folded into that mess later.

Doom and Rama Tut meet, deciding they may be the same person because they both have time machines.

Kang gets a lot more convoluted than this in the future.

Doom also posits that if his future self dies in the same time period as himself, then present-time Doom can't live in the present, so they decide against teaming up. 

Over with the Avengers we see our first use of time travel to change the course of recent history, done not by Immortus but by the Enchantress, who rewinds time to have a do-over so the Masters of Evil don't attack Earth's Mightiest Heroes.

In most instances in the Marvel Universe, going back in time to change the present is a futile effort, as it creates an alternate timeline and the original timeline you wanted to change remains. Usually. This case is unusual in that the Enchantress doesn't travel to the past - she rewinds time itself, presumably for all creation.

OR

She never mentions time travel, Zemo does. Her spell may have kept Marvel 616 on the same timeline, wiped everyone's mind, and recreated the world to be like it was in the past, all the while staying in the present.

Either way, this is far and away the most powerful thing the Enchantress has ever done, and it's done when a teleportation spell would have had the same result.

OR

She transported the Masters of Evil to an alternate Earth a few days ago, replacing the Masters of Evil there, possibly transporting them to this timeline where they are captured by the Avengers. This means that the Avengers of this issue (and presumably all previous issues) are a different timeline version than those in future issues

OR

By travelling to the past she created the alternate timeline, so there were one version of Avengers up to the beginning of this issue, with a split happening then, so that the Avengers prior to and after this issue are the same, but the ones in most of this issue are in a different timeline.

Marvel has had a lot of versions of time travel in their comics over the decades, and managed a brand new one in Endgame. Just don't ask me to explain Avengers Forever.