The events of a story take place in an eternal past / present / future that can be thought of as “narrative time.” Narrative time is not anchored to the unidirectional flow of time in which we live our lives. As a child one can read a story and follow the events as they unfold. As an adult one can read the same story and experience the same sequence and flow of events. Once complete the ending of the story does not become part of history as one can always reread it from the beginning.
Stories we tell in role playing also live in narrative time. As we move through linear time in session after session, we write the events of the story. Nevertheless, we can alway revisit earlier chapters, as players often do when recapping the last session before starting the current one. Storytellers sometimes borrow characters from one campaign for use in another, bringing the character as they appear at one point in the story into an entirely different narrative timeline.
Once they complete a campaign, players tend to speak about it in the past tense. One does not often repeat a previous campaign, so one might confuse the narrative time of the campaign with the linear time in which the sessions took place. On the other hand, insofar as the players are creators, the past tense may refer to production of the story rather than its events.
Role playing games take the form of a performance, one that may have artifacts like notes or maps associated even though the whole work is not fixed in a tangible medium of expression. When the performance is done, the players would sensibly speak of it in the past tense. The story told by their performance remains in narrative time, available for a future performance by these or other players. Translating the story of a campaign into a more tangible form requires realizing it in its narrative time. As a novel the campaign’s beginning and end become available simultaneously. As a game resource the story’s structure is flattened and laid bare, available for the past, present, or future of another campaign.