#timelinegate

But then the next morning Hopper comes to hear about the phone call and Joyce complains about him taking so long, and he says they were out searching all night ?

Is this two different timelines?

Hey, thanks for the ask!!! :D

I've seen this theory floating around. I think it’s cool, for sure...to me, the biggest pieces of evidence of the time travel/timelines are: 

The themes of time and “turning back the clock”. For example, Henry turns a clock backwards with his mind, the camera turns anticlockwise when El brings Max back to life, and there are 12 numbers on a clock. "Seconds, minutes, hours, days, years" etc.

The Upside Down is “stuck in time” on the day Will went missing. He went missing while dressed like Marty McFly. (His ST5 vest even looks like Marty’s future jacket). Along with that “Back to the Future” t-shirt you mentioned!!

Time discrepancies (e.g. birthdaygate). The anniversary effect, multiple important dates lining up w/ each other, Will’s forgotten/changed birthday.

I’ve personally interpreted this evidence in a more metaphorical way –

Characters’ memories of events/dates are being changed, therefore their “reality” is.

Characters are going to be “turning back the clock” by re-experiencing memories. Going back to 12 on the clock (perhaps age 12).

Similar to Eternal Sunshine of the Spotless Mind, the Truman Show etc.

But it could absolutely point to a more literal interpretation: time travel/alternate timelines!

The fabric of reality is actively being changed and rewritten, causing discrepancies with timelines.

Characters are going to travel in time or explore alternate timelines on their journey to set reality right.

Similar to Back to the Future, Donnie Darko etc.

I always find other people's time travel theories intriguing, and I wouldn't be mad if it ended up happening in the show. I think it could tell a satisfying story – if done right! The biggest thing would be the ending.

The Duffers have said themselves that they wouldn’t do the “it was all a D&D game” thing because the audience might feel cheated, and it might not be very satisfying. If the characters go back in time and erase everything, including all their memories, in my opinion this would be the same as that theory; not very satisfying. A bit like Umbrella Academy. “So it was all for nothing?” 

BUT, if the characters get to keep their memories of the original timeline, and/or only a few key things are changed, this would be a lot more satisfying for the audience. We’d all feel like we were in on a secret with our favourite characters, and it would feel like everything that happened was necessary for the ending.

It would be especially great if the concept of alternate timelines are explored through this, and we get to see a bunch of different versions of what could've happened in the show, had things gone differently. Henry’s “I became an explorer” line could be re-contextualised! Additionally, this would be an opportunity for the characters to accept the trauma that they've experienced through all their horrific adventures, and begin to move on, but MOST IMPORTANTLY – without erasing it from existence.

That's the biggest risk with the concept of resetting the timelines. If all the characters' memories are permanently erased, they don't grow, and they never actually work through the trauma of what happened, because it basically never happened at all. That's why, if there are time shenanigans, the main characters still need to remember!

...

So, the more metaphorical interpretation makes more sense to me personally, but I def wouldn’t discount the timelines theory. If you know any good analyses/evidence feel free to send ‘em my way!! I’m interested, especially if there’s maybe some evidence I haven’t considered before