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The specific order and/or accurate dates presented in this article has never been confirmed by Marvel Studios and/or Marvel Television, and therefore it can be inaccurate, incomplete, or partial.
This is a timeline of events that occurred during 2023.
- Massacre in Mexico: Clint Barton continued his mission of killing criminals who survived the Decimation by heading to Mexico and eliciting the entire Mexican Cartel.
- Steve Rogers becomes a grief counselor who gives therapy to a group of Decimation survivors.
- Natasha Romanoff and the remaining Avengers reside at the New Avengers Facility. Romanoff conducted a meeting via hologram with Nebula, Rocket, Okoye, Captain Marvel, and War Machine about the status of the universe. Rhodes notes that a certain someone has struck a cartel in South America, leaving no one alive.
- As Tony Stark plays with his daughter Morgan at his home, he discovers Morgan has gone into the garage and taken a helmet from something he had built for her mother, Pepper Potts.
- In a San Francisco storage unit, a rat inside Luis' Van walks into the panel's buttons and activates the Quantum Tunnel, causing Ant-Man to return from the Quantum Realm. After he is released with the help of a security guard, Scott Lang discovers the city is mostly abandoned. Fearful for his daughter, he checks a monument listing the victims of the Decimation, only to find his own name. Going to his ex-wife's house, Scott is greeted by a teenage Cassie Lang, who after being amazed that her father is still alive, hugs Scott.
- With Cassie's help, Scott crosses the country and goes to the Avengers Facility. Once he is welcomed inside, he details about a discovery made at the Quantum Realm: given it operates on its own time and space rules, the Realm can be explored and exploited to effectively time travel, opening the possibility of finding a way to reverse the Decimation.
- Scott, Steve and Natasha visit Tony. He refuses the proposal, feeling time travel is something too dangerous and unpredictable to even attempt. The trio's second option, Bruce Banner - now a "merged Hulk" retaining the green muscular form and Banner's personality - is initially skeptical, but agrees to help them experiment with the idea.
- Banner and Rocket visit "New Asgard" in Tønsberg, Norway to recruit Thor, who has become an obese, unkempt alcoholic and reduced his life to playing video games with Korg and Miek. Banner and Rocket eventually convince Thor to help them.
- After seeing a picture of himself with Spider-Man, Tony uses F.R.I.D.A.Y. to run different configurations for a time machine. One revolving around a Moebius strip turns out to be feasible.
- Tony returns to the Avengers Facility just as the first test using Scott goes wrong, in a way Stark later explains as "instead going through time, time went through Scott", making him turn into a child, an elder, and a baby prior to his regular self.
- Massacre in Tokyo: Hawkeye has found a Japanese Yakuza leader and has tracked him down to his stronghold. Here, the radicalized Clint kills every last one of the Yakuza including its leader: Akihiko. Clint then turns to find Natasha, who convinces him to return by explaining the Avengers' plan.
- Clint agrees to don the Advanced Tech Suit and test the time machine. He temporarily visits his homestead before his family was wiped out.
- Time Heist: After extensive group discussions, the Avengers decides to go back in time to retrieve the six Infinity Stones and use the combined set to undo the damage they had done. They are split into three groups: Scott, Steve, Bruce, and Tony head for 2012 New York City, as both the Space and Mind Stones were involved in the Battle of New York, and the Time Stone at the Sanctum Santorum; Thor and Rocket head for 2013 Asgard, where the Reality Stone was located prior to the Dark Elves' arrival; and Clint, Natasha, Rhodes, and Nebula head for planet Morag in 2014, with the former two leaving on the Benatar (which had been carried back miniaturized) to get the Soul Stone on Vormir, and the others staying to get the Power Stone before Star-Lord does so.
- Minutes after leaving, the Avengers return, with one exception: Natasha, who took upon herself to be the necessary sacrifice that summons the Soul Stone. Unbeknownst to the others, Nebula was actually the 2014 version with intense loyalty to Thanos, who intercepted her time traveler self back in the past.
- Reversal of the Decimation: A custom-made Infinity Gauntlet is equipped with all the Stones and then worn by Banner, who feels he is the only one powerful enough to perform the snap and survive. All life that had been wiped out returns, proven once Laura Barton calls her husband.
- Attack on the New Avengers Facility: While the other Avengers concluded their mission, the past Nebula executed her own. She hacks into the time machine and opens a portal back to 2014, allowing Thanos' flagship Sanctuary II to be transported into the future. The vessel then fired all its weapons on the headquarters, destroying it and the time machine, though all the Avengers survive.
- Following 2014 Thanos destroying the Avengers Facility, he thinks over his future self's victory and the Avengers' plan, deciding he will wipe away the universe to be the god of the next. This leads into a fight with Iron Man, Thor, and Captain America. Using a Mjølnir that Thor brought back from 2013, Rogers is able to one up Thanos for a time, until the latter gets a foothold and uses his sword to cleave Cap's shield in two.
- While his previous conquests have been detached of emotion, Thanos mentions he will enjoy erasing Earth, calling forth the full of his armies. Steve Rogers, still resolute, re straps what remains of his shield, and walks to confront Thanos and the Black Order.
- Battle of Earth: Following the Reversal of the Decimation, Doctor Strange used teleportation magic to summon a massive Avengers Allied Army throughput space and time: The Asgardians, Masters of the Mystic Arts, Ravagers, the Wakandan Armies, and the Guardians of the Galaxy. With their combined forces, they fight off Thanos's army. When Ant-Man remembers Luis' Van has a portal, the Avengers aim to use it to get rid of the Infinity Gauntlet, passing the Gauntlet across themselves on the way to the car. As Thanos orders an air strike, Captain Marvel returns to provide an assist, taking the gauntlet for a dash to the portal, but Thanos still destroys the van. As the Avengers do all they can to stop Thanos from getting the Infinity Gauntlet, it is when Thanos uses the raw power of the Power Stone to knock out Captain Marvel, that Stark gets an idea when Doctor Strange gestures that is related to the one outcome he saw where Thanos was defeated. Grabbing the gauntlet, Stark steals the Infinity Stones and equips them to his armor's glove.
- Using the combined power of the Infinity Stones, Tony Stark kills the time-travelling Thanos and his invading army, at the cost of his own life.
- Tony Stark dies and a funeral is held for him at his old home, where he is mourned by his family and heroes. 
- Thor leaves New Asgard under the care of Valkyrie, dubbing her New Asgard's new Queen before going to join the Guardians of the Galaxy.
- Returning the Stones: Steve Rogers is sent to return the Infinity Stones and Mjølnir to their original time periods. However, he does not return to the time machine. Instead, Rogers travels back to the 1940s and decides to stay in that period and spending the rest of his life with Peggy Carter. After a failed attempt by Bruce Banner to bring him back to normal, Bucky and Falcon see an old man sitting ahead the lake. Encouraged by Bucky, Sam come closer to that man understanding that he is an elderly Steve Rogers. After discussing with him, Cap delivers his now intact Shield to Sam.
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