Warning: Spoilers for Stranger Things season 4, volume 1!
In Stranger Things season 4's «Chapter Seven: The Massacre at Hawkins Lab,» it was confirmed that the Upside Down was stuck in 1983, and there are several reasons why. The Upside Down has been an integral setting in Stranger Things, serving as a mysterious alternate dimension parallel to the real world. When doors, or «gates,» have opened between the two dimensions, threats from the Upside Down leak into Hawkins, Indiana. At times, humans have been able to investigate the Upside Down, including houses and infrastructure that mirror Hawkins, albeit in a darker environment covered in spores, roots, and swirling ash-like dust.
Will Byers was the first person to spend ample time in the Upside Down and make it back to the real world. Though he was later confirmed to be the new host of the Mind Flayer, it confirmed that humans could travel throughout the alternate dimension. InStranger Things season 4, episode 7, «Chapter Seven: The Massacre at Hawkins Lab,» Nancy, Robin, and Eddie followed Steve through the «water gate,» leading to the Upside Down. With the threat of Demobats, Nancy suggested going to the Upside Down version of her house to retrieve her guns. While there, she discovered that the guns hidden in her room weren't there. This was because her guns hadn't existed yet, realizing through the diary in her room that the Upside Down was stuck in November 6, 1983.
Related: Stranger Things Season 4's Episode Lengths Are Ridiculous
The date of November 6, 1983, is significant in Stranger Things' Upside Down timeline for several reasons. First, it was the date that Dr. Martin Brenner requested that Eleven make contact with a «monster» with her telekinetic powers. Out
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