“The Mind Flayer?” Mike sighed. “No. It’s gone. Dustin’s been scanning every frequency. No sign.”

This gap marks a significant transition for the characters, moving from the winter of their 8th-grade year to the summer just before they enter high school as freshmen.

The gap between the end of Season 2 and the start of Season 3 is in-universe.

But time, unlike the Upside Down, kept moving.

April brought rain. So much rain that the quarry swelled and the woods turned to mud. Will and Mike biked to the arcade, but Will stopped drawing the shadow. He drew castles and dragons and nothing with tentacles. He tried so hard to be normal that his jaw ached from smiling.

“Too quiet,” Mike replied, and neither of them knew they were quoting the last line of a horror movie.

It was June 28th, 1985. And that was the answer.