Will Byers was in the Upside Down for about one week in Stranger Things season 1. In-story, he disappears on November 6, 1983, and is recovered on November 12, 1983, which lines up with what fans and timeline breakdowns discuss.

How long was Will in the Upside Down?

Most timeline-focused fans and forum discussions agree that Will is trapped in the Upside Down for roughly six days, often rounded to “about a week.” The date shown on-screen (November 12) when we see him in the library confirms that several days have passed since his disappearance on November 6.

  • Will is taken by the Demogorgon on November 6, 1983.
  • By November 12, he is hiding in the Upside Down and then found in the library with the tendril/demoslug in his mouth.
  • This places his total time in the Upside Down at around six days, often described as “about a week” in fan discussions and explainers.

Why “about a week” makes sense

The show never has a character say an exact hour count, but several contextual clues support the week-long duration:

  • In later dialogue, characters remark on how fast the town moved to hold a funeral, implying it had only been about a week since he went missing.
  • Fan analyses of diaries, calendar dates, and episode events consistently land between six and seven days for Will’s time there.

How he survived that long

Viewers often question how Will survived nearly a week with little visible food or water:

  • Some fans speculate that the Upside Down’s atmosphere and strange biology might slow human metabolism, helping a person last longer with minimal resources.
  • Others point to the demoslug/parasite as possibly altering his body and keeping him barely alive, along with the toxic air contributing to his weakened, near-death state when Joyce and Hopper find him.

In short: within the show’s internal timeline, Will is trapped in the Upside Down for roughly six days, commonly described as about a week.

TL;DR: Will was trapped in the Upside Down for around six days —from November 6 to November 12, 1983—so fans usually summarize it as “about a week.”

Information gathered from public forums or data available on the internet and portrayed here.