Take place in Earth-616.
The title/publishing of One More Day took starts in issue number #544 of the Amazing Spider-Man, in Friendly Neighborhood Spider-Man issue #24 and The Sensational Spider-Man (Volume 2) issue #41 , and finally ends in Amazing Spider-Man #545.
One More Day begins in Amazing Spider-Man #544, where Peter Parker's Aunt May is shown slowly dies from a gunshot wound sustained during the events of Civil War event and the Back in Black storyline.
However, Peter seeks the aid of several others including Doctor Doom, the High Evolutionary, Reed Richards, and even Doctor Octopus. Peter even attempts to go back in time using a magic spell without Doctor Strange's approval, hurting himself in the process. Doctor Strange heals his wounds and sends him on his way, encouraging him to just be by Aunt May's side at her death.
On his way to the hospital, Peter is confronted by a little girl, who says she holds the answer to his problem. He talks to the little girl, who runs off. While running after her, Peter encounters a group of men, and a woman in red informs him these are alternate versions of himself, from alternate realities where they never became Spider-Man. The woman in red transforms into the demon Mephisto, who tells Peter he can save Aunt May. As payment, Mephisto wants not Peter's soul, but the history of his marriage with Mary Jane. That same day, Peter and Mary Jane are given until midnight the following night to decide their answer and, after several hours agonizing over the choice, they agree to the deal, as long as knowledge of Peter's secret identity is erased from the entire world.
Mary Jane also whispers to Mephisto another, unspecified offer in return for Mephisto putting Peter's life back exactly how it was and "giving him a chance at happiness." Finally, Mephisto reveals to the couple that his disguise as the little girl was in fact their future daughter, May Parker, but she will never exist because of their choice.
Mephisto then changes history so that Peter and Mary Jane were never married, and no one remembers whose face is underneath Spider-Man's mask. Peter wakes up alone in bed, once again living with Aunt May. He goes a party being held for his best friend Harry Osborn (who was previously thought to have died in Spectacular Spider-Man #200), who introduces Lilly Hollister and Carlie Cooper. Afterwards, Peter views Mary Jane sadly leaving the party. The comic and storyline end with all the guest toasting to a "Brand New Day."
- The One More Day storyline take place after the Civil War event, and Back in Black storyline but before the Brand New Day storyline.