The scene where a government helicopter is briefly mistaken for some otherworldly phenomenon echoes a similar scene in Close Encounters of the Third Kind (1977).
This is the shortest runtime out of all episodes of season 4 of "Stranger Things" (2016) clocking in at 1hr. 3mins.
When Nancy and Robin go to the library, the picture on the wall to the right of the door is a poem from "The Light in the Attic" by Shel Silverstein called "Overdues."
This episode takes place from March 22 to March 23, 1986.